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A  TREATISE 


LIGHTNING  CONDUCTORS; 

COMPILED  FROM 

A  WORK  ON  THUNDERSTORMS,  BY 
S.  W.  HARRIS,  F.R.S., 

AND  OTHER 


STANDARD  AUTHORS. 


BY 

LUCIUS  LYON,  A.M. 


NEW- YORK : 

GEORGE  P.  PUTNAM,  10  PARK  PLACE. 


M.DCCO.LIII 


A 

Entered,  according  to  Act  of  Congress,  in  the  year  1853,  by 
Lucixjs  Lyon,  A.  M., 

in  the  Clerk’s  Office  of  the  District  Court  for  the  Southern  District  of 

New-York. 


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PREFACE. 


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It  is  not  a  little  remarkable,  when  we  consider  the 
prevailing  disposition  of  the  times  to  apply  the  dis¬ 
coveries  of  natural  science  to  useful  purposes,  and  to 
embody  them  in  those  material  forms  which  make 
them  subservient  to  the  wants  of  man,  that,  among 
^  the  books  which  are  incessantly  issuing  from  the 
press,  none  has  yet  appeared,  in  this  country,  ex- 
^clusively  devoted  to  the  subject  of  practical  elec¬ 
ts  tricity.  Theoretically,  indeed,  the  study  of  the  phe¬ 
nomena  of  electricity  awakens  a  lively  interest  in 
j  i  every  mind,  both  on  account  of  the  wonderful  de- 
fo  velopments  which  are  constantly  made,  and  the 
^  subtle  and  mysterious  nature  of  its  essence ;  seeming, 
as  it  does,  to  occupy  the  internal  between  mind  and 
matter;  but,  since  the  brilliant  experiment  of  Dr. 


IV 


PREFACE. 


Franklin,  identifying  lightning  with  electricity,  al¬ 
though  much  information  has  been  acquired,  both  in 
this  country  and  abroad,  no  treatise  has  been  pub¬ 
lished,  exhibiting  to  the  American  reader  those  facts 
which  are  necessary  for  his  guidance,  in  applying 
the  discovery  of  Franklin  successfully  to  the  protec¬ 
tion  of  life  and  property. 

The  only  explanation  of  this  circumstance  which 
can  be  given  is,  that  the  construction  and  applica¬ 
tion  of  lightning  conductors,  has  appeared  to  most 
persons  a  matter  too  simple  to  need  any  aid  from 
books,  while  hot  a  few  have  looked  upon  the  whole 
theory  as  absurd,  and  as  a  source  of  danger  rather 
than  of  safety.  There  has  been,  consequently,  but 
little  encouragement  for  the  compiling  of  a  work 
calculated  to  bring  before  the  community  all  that 
has  been  learned  on  this  subject. 

The  various  systems  of  rodding,  however,  which 
have  sprung  up  of  late,  and  the  different  modifica¬ 
tions  of  the  conductor,  which  have  been  patented 
and  presented  to  the  public,  each  claiming  some 
peculiar  advantage  over  all  its  competitors,  have 
created  a  curiosity,  if  not  a  necessity,  which  seems  to 
justify  the  publication  of  the  present  volume. 

The  valuable  treatise  recently  publislied  in  Lon¬ 
don,  from  the  pen  of  S.  W.  Harris,  F.  E.  S.,  is  quite 


PREFACE. 


V 


too  expensive  to  admit  of  general  circulation ;  and 
it  is  thought,  too,  that  one  less  extended  will  be 
better  adapted  to  the  wants  of  the  American  public. 
The  compiler  of  the  following  work  has,  therefore, 
aimed  to  comprehend  within  reasonable  limits  all 
the  facts  that  are  essential,  omitting  such  details  as 
are  merely  curious,  or  such  as  suggest  no  new  and 
valuable  application  of  science.  He  has  made  a  free 
use  of  all  the  materials  within  his  reach,  referring, 
for  the  satisfaction  of  the  reader,  as  well  as  injustice 
to  his  authorities,  to  the  book  and  page  from  which 
they  have  been  derived. 

There  can  be  no  doubt  of  the  utility  of  such  a 
book  as  is  here  presented.  After  expending  large 
sums  of  money  for  the  most  approved  apparatus  of 
rods,  many  persons  have  been  bitterly  disappointed 
in  their  expectations,  and  have  received  no  adequate 
return  for  their  outlays.  The  truth  is,  that  our 
countrymen  have  not  acted  on  this  subject  with  that 
shrewdness  for  which,  in  other  things,  they  are  pro¬ 
verbial.  They  have  taken  too  much  upon  trust,  and 
neglected  the  investigation  of  the  facts.  The  iron 
conductors,  put  up  at  no  inconsiderable  cost,  and 
supposed  to  secure  perfect  safety  to  the  structures 
which  they  surmount,  instead  of  proving  themselves 
faithful  sentinels  and  guardians  in  the  hour  of  peril, 


I 


VI 


PREFACE. 


have  too  often  turned  traitors,  and  invited  the  de¬ 
struction  which  they  promised  to  avert.  The  “swift 
fire  of  Jove,  hurled  by  his  red  right  arm,”  has  not 
unfrequently  bolted  from  the  iron  track,  prepared 
for  its  harmless  descent,  and,  indignant  at  some  de¬ 
fective  joint,  or  sudden  break,  or  the  want  of  suf¬ 
ficient  metal  for  its  free  discharge,  has  made  a 
forcible  passage  for  itself,  often  leaving  shattered 
walls,  and  chimneys,  and  blazing  roofs,  to  attest  its 
terrific  power.  Happy  for  the  sufferers  if  the  blasted 
corpse  of  some  loved  one  has  not  added  unutterable 
woe  to  the  desolation  of  the  scene ! 

Such  disastrous  consequences  are  due,  in  part, 
to  imposture,  but  far  more  frequently  to  the  igno- ' 
ranee  and  carelessness  of  workmen,  and  to  the  blind 
credulity  of  those  who  have  employed  them.  In 
many  instances,  too,  the  owners  of  property  have 
suffered  an  apparatus,  originally  well  adjusted,  to 
get  out  of  repair.  The  distrust  which  might  have 
arisen  from  these  accidents,  has  no  doubt  been  miti¬ 
gated  or  prevented,  in  a  great  degree,  by  the  difih- 
culty  of  detecting  any  defect  in  a  system  of  con¬ 
ductors — a  philosophical  knowledge  of  the  sci¬ 
ence  of  electricity  often  being  requisite  for  doing 
so. 

Partly  from  the  imperfectious  alluded  to  above, 
but  much  more  from  the  unaccountable  apath}^  which 


PREFACE. 


Vll 

exists  on  the  whole  subject,  a  very  large  proportion 
of  the  owners  of  buildings  in  this  country,  and  proba¬ 
bly  a  still  greater  proportion  in  other  countries,  have 
neglected  to  avail  themselves  of  the  lightning  con¬ 
ductor  in  any  form.  An  incalculable  amount  of 
property,  and  many  lives,  which  might  be  made  at 
least  relatively  secure,  are  thus  constantly  and  need¬ 
lessly  jeopardized.  How  great  a  risk  is  incurred, 
and  how  nearly  absolute  safety  is  attainable  by  con¬ 
ductors,  the  author  hopes  to  demonstrate  in  the  fol¬ 
lowing  pages. 

Mr.  Harris,  in  his  unrivalled  work  on  Thunder¬ 
storms,  has  the  following  appropriate  Introduc¬ 
tion  : 


“  The  fact  of  electrical  conduction  by  metallic  substances 
having  been  so  long  and  so  well  established,  any  further  dis¬ 
cussion  of  the  application  of  this  principle  to  the  purpose  of 
protection  against  lightning  may  possibly  appear  to  persons, 
conversant  with  such  subjects,  as  in  some  degree  superfluous. 
The  damage,  however,  which  so  frequently  occurs  in  thun¬ 
derstorms,  attended  as  it  is  with  loss  of  life,  and  with  serious 
inconvenience  to  the  best  interests  of  the  country,  may  be 
fairly  adduced  as  a  sufficient  reply  to  such  an  opinion. 

“The  beautiful  spire  of  St.  Martin’s  church,  in  London, 
has  been  recently  rebuilt,  at  a  cost  of  full  one  thousand 
pounds  sterling,  in  consequence  of  an  explosion  of  lightning. 


Vlll 


PREFACE. 


which  fell  on  it  in  July  last.  Brixton  church,  near  London, 
had  also  to  undergo  extensive  repairs,  rendered  necessary 
from  the  same  cause.  In  January,  1841,  the  spires  of  Spit- 
alfields  and  Streatham  churches,  were  struck  by  lightning, 
and  the  latter  nearly  destroyed ;  and  in  August  of  the  same 
year  an  electrical  discharge  shook  the  spires  of  St.  Martin’s 
and  St.  Michael’s  churches,  at  Liverpool,  both  modern  edi¬ 
fices  of  a  costly  and  elaborate  construction.  In  January, 
1836,  the  spire  of  St.  Michael’s  church,  near  Cork,  was  rent 
by  lightning  down  to  its  very  base;  and  in  the  following 
October  the  magnificent  spire  of  Christ  church,  Doncaster, 
was  almost  totally  destroyed  by  a  similar  discharge. 

“  Thus,  in  the  United  Kingdom  alone,  and  within  the 
short  space  of  five  years,  we  find  at  least  eight  churches  to 
have  been  either  severely  damaged  or  partially  demolished 
by  lightning ;  to  this  list  of  casualties  may  be  added  the 
fine  old  church  of  Exton,  in  Rutland,  which,  according  to  the 
public  journals,  was  in  great  measure  destroyed  in  a  thunder¬ 
storm,  so  lately  as  the  25th  of  last  April.  A  writer  in 
Nicholson’s  Journal  of  Science,  states  that  he  has  made  a 
calculation  of  the  average  annual  amount  of  damage  done 
by  lightning  in  England  alone,  and  that  it  cannot  be  far  short 
of  fifty  thousand  pounds. 

“  In  the  British  Navy  the  eftects  of  lightning  have  been 
most  disastrous.  Since  the  commencement  of  the  war  in 
1793,  more  than  two  hundred  and  fifty  ships  are  known  to 
have  suffered  in  thunderstorms.  It  is  not  possible  to  state 
with  any  degree  of  precision  the  total  amount  of  damage 


PREFACE. 


IX 


done,  as  all  the  instances  in  which  ships  have  snfiered  cannot 
he  well  ascertained ;  some  idea,  however,  may  be  formed  of 
it  from  the  following  facts,  derived  from  the  official  journals 
of  Her  Majesty’s  ships,  deposited  at  the  Admiralty.  In  one 
hundred  and  fifty  cases,  the  majority  of  which  occurred  be¬ 
tween  the  years  1799  and  1815,  nearly  one  hundred  lower 
masts  of  line-of-battle  ships  and  frigates,  with  a  correspond¬ 
ing  number  of  topmasts  and  smaller  spars,  together  with  va¬ 
rious  stores,  were  wholly  or  partially  destroyed.  One  ship 
in  eight  was  set  on  fire  in  some  part  of  the  rigging  or  sails ; 
upwards  of  seventy  seamen  were  killed,  and  one  hundred  and 
thirty-three  wounded,  exclusive  of  nineteen  cases  in  which 
the  number  of  wounded  is  returned  as  ‘  many  ’  or  ‘  sever¬ 
al.’  In  one-tenth  of  these  cases  the  ships  were  completely 
disabled,  and  they  were  compelled  in  many  instances  to 
leave  their  stations,  and  that  too  at  a  critical  period  of  our 
history.  The  expenditure  in  these  few  cases  in  the  mere 
material,  could  not  have  been  far  short  of  one  hundred  thou¬ 
sand  pounds  sterling.  So  that  if  the  whole  amount  of  the 
loss  to, the  public,  in  men,  in  money,  and  in  services  of  ships, 
could  be  ascertained,  it  would  necessarily  prove  to  be  enor¬ 
mous  ;  more  especially  when  we  take  into  account  the  ex¬ 
pense  of  the  detention  and  refit  of  the  damaged  vessels,  the 
average  cost  of  a  single  line-of-battle  ship  to  the  country 
being  one  hundred  pounds  per  diem  and  upwards.  Now 
between  the  years  1809  and  1815,  that  is  to  say,  within  the 
short  period  of  six  years,  full  thirty  sail  of  the  line,  and  fif¬ 
teen  frigates,  were  more  or  less  disabled. 

1% 


X 


PREFACE. 


“  A  very  considerable  portion  of  this  mass  of  destruction 
occurred,  it  is  true,  at  a  time  when  a  great  number  of  ships 
were  required  ;  but  at  a  more  recent  period,  in  time  of  peace, 
when  the  Navy  has  been  greatly  reduced,  we  find  a  large 
amount  of  these  casualties  to  be  constantly  occurring.  On 
the  Mediterranean  station  alone,  between  the  years  1838  and 
1840,  the  Rodney^  Powerful,  Ceylon,  Tribune,  Scorpion, 
Wasp,  Tyne,  and  Blazer,  were  struck  by  lightning,  and 
many  of  them  severely  damaged  :  the  Rodney,  in  addition 
to  the  destruction  of  her  mainmast,  was  set  on  fire.  In  little 
more  than  twelve  months,  about  the  year  1830,  three  line- 
of-battle  ships,  a  frigate,  and  a  brig,  were  also  more  or  less 
disabled.  In  other  parts  of  the  world  we  have  lately  had 
the  Rhadamanthus,  Gorgon,  Snake,  Racehorse,  Pique,  aTid 
many  others,  damaged  by  lightning;  and  in  1832,  the  South¬ 
ampton,  of  fifty  guns,  narrowly  escaped  being  blown  up  in 

the  Downs. 

« 

“  It  has  been  suggested  that  many  ships  reported  as 
‘missing,’  have  been  destroyed  in  thunderstorms,  a  surmise 
almost  converted  into  a  reality,  by  the  ravages  which  light¬ 
ning  is  known  to  be  capable  of  producing.  From  a  refer¬ 
ence  to  the  official  log  of  the  Lacedoemonian,  and  to  the  evi¬ 
dence  of  Admiral  Jackson,  who  then  commanded  her,  it  ap¬ 
pears,  that  His  Majesty’s  ship  Peacock  disappeared  during  a 
violent  storm  of  lightning  on  the  coast  of  Georgia,  in  the 
year  1814.  The  Loup  Cervier,  another  of  His  Majesty’s 
ships,  was  last  seen  off  Charlestown,  on  the  evening  of  a  se¬ 
vere  thunderstorm,  and  has  not  since  been  heard  of.  When 


PREFACE. 


XI 


His  Majesty’s  ship  Resistance,  of  forty-four  guns,  was  blown 
up  by  lightning  in  the  Straits  of  Malacca,  in  the  year  1798, 
two  or  three  of  the  crew  were  picked  up  by  a  Malay  proa, 
which  happened  to  be  in  company ;  but  for  this  circum¬ 
stance,  the  fate  of  this  ship  would  have  remained  in  the  same 
obscurity  which  now  hangs  over  so  many  vessels  reported 
as  ‘  missing,’  as  all  the  rest  of  the  crew  perished. 

“  The  journals  of  the  ships  of  the  Honorable  East  India 
Company  furnish  appalling  statements  of  the  damage  and 
loss  of  life,  caused  by  the  electrical  explosions  which  have 
fallen  on  them,  while  freighted  with  the  rich  products  of  the 
East :  even  so  lately  as  1842,  the  Coote,  of  twenty  guns,  one 
of  the  navy  of  this  great  mercantile  power,  had  her  masts 
shivered  in  pieces  by  lightning  at  Madras. 

“  Though  we  have  not  the  same  means  of  ascertaining 
the  damage  done  to  our  mercantile  marine,  yet  the  loss  to 
the  shipping  interest,  in  consequence  of  lightning,  must  be 
extremely  great.  Scarcely  a  year  passes,  without  a  calami¬ 
tous  account  appearing  in  the  public  prints,  of  some  fine 
merchant  ship  having  been  damaged  or  totally  destroyed. 
In  March  last,  the  Toronto,  one  of  the  splendid  packets  which 
sail  between  London  and  New-York,  was  struck  by  light¬ 
ning,  which  killed  one  of  the  crew,  and  damaged  the  vessel ; 
and  in  August,  1842,  the  Defiance,  a  large  transport  laden 
with  Government  stores,  including  rockets  and  gunpowder, 
had  her  mainmast  completely  rent  through  to  the  keel  by 
an  electrical  dischaige  off  Nankin;  the  ship  was  filled  with 
a  sulphurous  smoke,  and  the  greatest  consternation  prevailed 


XJl 


PREFACE. 


among  the  troops  and  seamen,  from  the  dread  of  an  imme¬ 
diate  explosion.  In  May,  1840,  the  ship  Madras  was  set  on 
fire,  and  a  portion  of  her  side  was  driven  out  by  an  electrical 
explosion,  and  in  1839  a  similar  accident  befel  a  large  barque 
called  the  John  and  James  off  Algiers,  so  that  she  was  with 
difficulty  prevented  from  sinking.  In  1838,  the  Orwell^  a 
large  trader  laden  with  cotton,  was  set  on  fire,  and  narrowly 
escaped  total  destruction.  Within  a  few  years  the  merchant 
ships  Tanjore^  Poland,  Logan,  Ruthella,  Bolivar,  Boston, 
and  Lydia,  are  known  to  have  been  entirely  consumed. 

“  However  well,  therefore,  the  fact  of  electrical  conduc¬ 
tion  may  be  known, — however  well  scientific  men  may  be 
agreed  that,  by  the  judicious  employment  of  metallic  bodies, 
we  may  ensure  protection  against  lightning, — certain  it  is 
that  the  principle  itself  is  far  from  being  generally  under¬ 
stood,  or  universally  adopted.  Indeed,  to  existing  prejudices 
arising  entirely  out  of  a  misapprehension  of  the  laws  of  elec¬ 
trical  discharge,  may  be  traced  the  great  destruction  of  life 
and  property  so  frequently  occurring  from  the  effects  of 
lightning. 

“  It  is  not  easy  to  explain  how,  in  the  present  advanced 
state  of  natural  knowledge,  so  many  anomalous  views  and 
opinions  on  this  interesting  subject  should  pervade  the  public 
mind,  since  in  no  department  of  physical  science  is  the  field 
of  observation  more  fertile,  or  the  path  of  experience  more 
direct  and  certain.  We  have  at  our  command  the  results 
of  observation  for  nearly  a  century,  during  which  time  light¬ 
ning  rods  have  been  employed ;  a  great  many  instances  are 


PREFACE. 


Xlll 

to  be  found,  in  wliicli  lightning  has  fallen  on  buildings  un¬ 
der  a  variety  of  peculiar  circumstances.  In  some  cases  light¬ 
ning  rods  have  been  present,  in  others  not:  moreover,  we 
can  successfully  imitate  by  artificial  means  the  gi’eat  opera¬ 
tions  of  nature,  and  examine  experimentally  every  probable 
result  of  a  shock  of  lightning,  and  every  possible  contingency 
attendant  on  it.  We  ought,  therefore,  to  find  no  difficulty  in 
arriving  at  a  practical  solution  of  such  questions  as  these : — 
Is  the  application  of  a  lightning  conductor  desirable  in  any 
particular  case  ?  May  it,  by  a  species  of  attractive  force  in¬ 
herent  in  it,  cause  a  discharge  of  lightning,  which,  otherwise, 
would  not  have  occurred  in  this  particular  direction  ?  If  so, 
may  it  occasion  the  damage  it  was  set  up  to  avert,  through 
its  inability  to  meet  the  explosion  that  may  fall  on  it  ?  Is  it 
liable  to  produce  destructive  effects,  by  any  species  of  lateral 
discharge  of  the  electricity  in  passing  along  it  ?  vVhat  are 
the  best  dimensions  and  form  of  a  lightning  conductor  ?  and 
such  like.  If  such  questions  as  these  cannot  now  be  deter¬ 
mined,  they  in  all  probability  never  will  be.” 


Now  if  this  unpretending  volume,  by  attracting 
a  more  careful  attention  to  practical  electricity,  and 
by  diffusing  in  this  community  all  the  important  in¬ 
formation  that  has  yet  been  elicited  on  this  subject, 
shall  be  the  means,  under  God,  of  preserving  the 
property  of  any  individual,  or  of  preventing  the  loss 
pf  a  single  life,  the  author  will  feel  that  the  time  and 


XIV 


PREFACE. 


labor  devotea  to  its  preparation  will  be  amply  com¬ 
pensated  by  the  amount,  however  small,  thus  contri¬ 
buted  to  the  sum  of  human  happiness. 

Lucius  Lyon. 


CONTENTS. 


SECTION  I. 

GENERAL  VIEW  OF  NATURAL  AND  ARTIFICIAL  ELECTRICITY. 

Electricity  considered  in  relation  to  common  matter,  3.  Electrical 
conditions  of  a  thunderstorm,  12.  Insulation — Conduction — 
Charge — ^Discharge,  <fec.,  IT.  Identity  of  common  electricity 
with  the  agency  of  lightning,  23.  Nature  of  ordinary  electrical 
arrangements  producing  artificial  lightning,  27.  Various  phe¬ 
nomena  of  lightning  and  thunder,  34.  Appearances  termed 
fire-balls,  38.  Sulphurous  odor  of  the  electric  discharge,  42. 
Artificial  disruptive  discharges,  44.  Further  observations  on 
thunder-clouds,  49.  Electrical  discharges,  52.  Ascending  or 
upward  stroke,  59. 


SECTION  II. 

APPLICATION  OF  METALLIC  CONDUCTORS  TO  THE  DEFENCE 
OF  BUILDINGS  AND  SHIPPING  FROM  LIGHTNING. 


Laws  and  operation  of  disruptive  discharge,  69.  Observed  effects  on 
buildings  and  ships,  74.  St.  Martin’s  church  struck  by  light- 


XVI 


CONTENTS. 


ning,  76.  Brixton  church  struck  by  lightning,  83.  Nature  of 
lightning  rods,  89.  Laws  of  electrical  conduction,  92.  Mechani 
cal  effects  of  the  electrical  discharge,  94.  What  quantity  of 
metal  is  requisite  for  a  lightning  rod?  105.  How  far  does  the 
protecting  power  of  a  lightning  rod  extend  ?  110. 


SECTION  III. 

EESULTS  OF  THE  APPLICATION  OF  LIGHTNING  RODS  TO 
BUILDINGS  AND  SHIPS. 

FROM  THE  PERIOD  OF  THEIR  FIRST  BEING  EMPLOYED  IN 
THE  YEAR  1760. 

Introductory  remarks,  117.  Whether  lightning  rods  and  other  me¬ 
tallic  conductors  have  effectually  guarded  buildings,  <fec.  against 
damage  by  lightning?  118.  Whether  lightning  rods  attract 
lightning?  132.  Whether  in  certain  cases  pointed  condnctors 
actually  prevent  explosions  of  lightning  from  falling  on  build¬ 
ings  ?  141.  Phenomena  observed,  when  a  dense  explosion  of 
electricity  falls  on  a  lightning  rod,  152.  Harmless  character  of 
the  luminous  appearances  observed  on  lightning  rods,  154. 
Division  of  the  charge,  156.  Instances  in  which  buildings  pro¬ 
vided  with  pointed  conductors  are  said  to  have  been  damaged 
by  lightning,  158.  Precautions  when  exposed  to  the  action  of 
thunderstorms,  ]70.  Construction  of  lightning  rods  applied 
to  buildings,  171.  Practical  deductions,  184.  Concluding  ob¬ 
servations,  187. 


SECTION  I 


GENERAL  VIEW  OF  NATURAL  AND 
ARTIFICIAL  ELECTRICITY. 


Electricity  considered  in  relation  to  common  matter — Conditions  of 
a  Thunderstorm — Insulation — Charge— Conduction— Discharge, 
&c. — Identity  of  Natural  and  Artificial  Electricity — Nature  of 
ordinary  Electrical  arrangements  producing  Disruptive  Dis¬ 
charge — Various  Phenomena  of  Thunder  and  Lightning — Ap¬ 
pearances  termed  Fire  Balls — Sulphurous  odor  of  the  Electrical 
Discharge — Artificial  discharges  of  various  kinds — Luminous 
appearances  similar  to  those  in  Nature — Further  observations 
on  Thunder  Clouds — Electrical  Discharges — Possible  Causes  of 
Discharge — Upward  Dischai-ge. 


i. 


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NATURAL 

AND 

ARTIFICIAL  ELECTRICITY. 


Electricity  considered  in  relation  to  Common  Matter. 

Before  entering  upon  the  subject  of  the  application 
of  metallic  substances  to  buildings  and  ships,  with  a 
view  to  their  protection  from  lightning,  it  may  not 
be  unimportant  to  review  the  amount  of  information 
we  are  in  possession  of,  relative  to  the  nature  and 
operation  of  thunderstorms. 

A  large  induction  of  facts,  leaves  little  doubt  of 
the  existence  of  some  elementary  or  primordial  prin¬ 
ciple  in  nature,  every  where  present,  and  intimately 
associated  with  the  particles  of  common  matter,  ac¬ 
cording  to  some  general  law.  In  what  this  element 
consists,  we  are  quite  ignorant ;  we  know,  however, 
that  there  is  such  a  constituent  principle,  and  that  it 
is  capable  of  exerting,  under  given  circumstances,  an 
all-powerful  action  ;  hence  it  may  be  considered  as  a 


4 


ELECTRICITY  CONSIDERED 


species  of  unknown  physical  force  or  agency,  the 
laws  of  which  it  is  our  business  to  investigate. 

Now  it  is  no  objection  to  the  practical  results  of 
such  an  inquiry,  to  say  that  we  are  ignorant  of  the 
nature  of  the  agency  with  which  we  are  dealing — it 
being  the  great  end  of  modern  philosophy  rather  to 
trace,  and  apply  the  uniform  relations  of  certain 
facts,  than  to  speculate  upon  the  nature  of  the  mys¬ 
terious  causation,  upon  which  the  connection  de¬ 
pends.  Thus  Newton  was  content  to  examine  the 
laws  of  gravity,  and  the  relations  of  this  force  to 
common  matter,  without  in  any  way  meddling  with 
its  nature  as  an  occult  cause ;  and  from  this  method 
of  inquiry  the  happiest  consequences  have  resulted. 
The  same  method  is  equally  applicable  to  the  subtle 
principle  active  in  a  thunderstorm :  we  may  arrive 
at  all  the  practical  information  we  require  relative  to 
this  grand  yet  fearful  display  of  its  powers,  even 
although  we  should  never  understand  its  nature  as  a 
primary  source  of  causation. 

This  physical  force  or  agency  has  been  termed 
electricity,*  and  there  is  some  strong  evidence  for 
supposing  it  to  be  an  extremely  attenuated  and 
subtle  kind  of  matter — differing,  however,  in  its 
properties  from  any  form  of  matter  of  which  we 
have  cognizance. 

It  is  insensible  to  ordinary  perception  so  long  as 
it  is  distributed  amongst  the  particles  of  bodies  ac- 

*  The  Greeks  observed  its  effects  in  amber,  ¥i\^Krpov,  hence  the 
term. 


\ 


IN  RELATION  TO  COMMON  MATTER. 


5 


cording  to  a  given  law.  In  this  state  it  is  said  to  be 
neutral,  or  inactive;  when,  however,  the  equilibri¬ 
um  of  distribution  is  from  any  cause  disturbed,  then 
a  variety  of  interesting  phenomena  begin  to  appear, 
and  the  electrical  agency  manifests  a  tendency  to  re¬ 
turn  to.  its  previous  state  of  quiescence. 

A  variety  of  natural  and  artificial  operations 
affect  the  neutral  electrical  state  of  matter.  Under 
natural  operations,  may  be  classed  changes  em- 
perature,  changes  in  the  form  of  bodies,  chemical 
changes,  &c. ;  thus  brimstone,  chocolate  fresh  from 
the  mill,  wax,  resin,  &c.,  when  melted,  become  elec¬ 
trical  in  cooling ;  the  tourmalin,  also,  and  many 
other  substances,  evince  electrical  signs  under  a 
change  of  temperature.  In  the  decomposition  of 
water,  by  means  of  sulphuric  acid  and  zinc,  we  find 
the  bottle  in  which  the  chemical  action  is  proceeding 
strongly  electrical ;  and  it  is  a  remarkable  fact,  that 
during  the  progress  of  thunderstorms,  the  vapor  of 
the  atmosphere  is  condensed  into  rain,  or  frozen  into 
hail,  and  the  general  temperature  of  the  air  altogether 
changed. 

Hence,  from  the  sum  of  our  knowledge  respect¬ 
ing  meteorological  phenomena,  there  appears  great 
reason  to  conclude,  that  the  causes  which  produce 
artificial  electricity  are  all  in  full  operation  in  the 
masses  of  vapor,  among  which  natural  electricity 
appears  active. 

This  opinion  is  maintained  by  several  eminent 
electricians  of  the  present  day.  It  was  warmly  es¬ 
poused  by  the  late  Mr.  Singer,  who  advanced  in 


6 


ELECTRICITY  CONSIDERED 


support  of  it  the  following  positions :  (1.)  That  the 

electrical  phenomena  of  the  atmosphere  take  place, 
in  all  climates,  to  the  greatest  extent,  about  the 
period  of  the  greatest  degree  of  heat,  when  the  rays 
of  the  sun  have  caused  a  considerable  accumulation 
of  vapor.  (2.)  Where  this  cause  operates  to  the 
greatest  extent,  as,  for  instance,  within  the  tropics, 
natural  electricity  is  produced  on  the  largest  scale. 
(3.)  j^hen  the  natural  source  of  evaporation  is 
assisted  by  collateral  causes,  electrical  changes  occur 
with  astonishing  activity,  as  in  the  eruption  of  a 
volcano,  or  the  heat  imparted  to  the  air  in  its  pas¬ 
sage  over  large  extents  of  hot  sands,  as  those  of 
Africa.  (4.)  By  the  action  of  winds,  currents  of  air 
of  different  temperatures  are  often  mixed,  so  that 
such  as  have  been  heated  and  charged  with  moisture, 
become  suddenly  cooled,  thus  occasioning  a  precipi¬ 
tation  of  water,  and  the  occurrence  of  electrical 
changes.  This  is  often  witnessed  on  the  coast  of 
Guinea  during  the  existence  of  the  Harmattan. 
(5.)  These  electrical  changes  are  every  where  most 
frequent  when  the  causes  of  evaporation  and  conden¬ 
sation  suddenly  succeed  each  other. 

After  advancing  several  cogent  arguments  in 
favor  of  the  above  facts,  and  noticing,  in  a  very  can¬ 
did  manner,  some  objections  urged  against  the  theo¬ 
ry  they  are  intended  to  support,  Mr.  Singer  con¬ 
cludes  with  the  following  truly  appropriate  and 
judicious  observations: — “Although  the  immediate 
causes  by  which  the  various  phenomena  of  the  at¬ 
mosphere  are  produced,  be  still  far  beyond  our  com- 


IN  RELATION  TO  COMMON  MATTER. 


7 


prehension,  yet  the  connection  of  their  several  effects 
is  a  sufficient  demonstration  that  they  are  not  purely 
mechanical,  but  subservient  to  the  direction  of  su¬ 
preme  power  and  intelligence.  By  this  means,  the 
most  simple  arrangement  becomes  the  source  of  sub¬ 
lime  effects.  The  process  of  evaporation  which 
modifies  the  action  of  the  sun’s  rays,  and  conveys  to 
every  part  of  the  earth’s  surface  a  source  of  fertility, 
does  at  the  same  time  diversify  the  appearance  of 
the  atmosphere  by  an  endless  variety  of  imagery, 
enlivening  the  horizon  with  the  most  brilliant  and 
glowing  tints,  and  in  all  probability  effecting  those 
electrical  changes  which  are  the  precursors  of  the 
most  magnificent  phenomena  in  nature.” 

Under  artificial  operations  may  be  classed  fric¬ 
tion,  pressure,  and  other  mechanical  actions: — the 
electrical  machine,  essentially  a  plate  or  cylinder  of 
glass,  made  to  revolve  between  or  against  fixed 
cushions,  is  sufficiently  illustrative  of  this — we  ob¬ 
serve  brilliantly  luminous  sparks  fly  round  the 
glass,  and  dart  off  from  a  metallic  substance  opposed 
to  it,  in  consequence  of  the  disturbed  state  of  the 
electrical  distribution  in  these  bodies. 

Amongst  the  various  relations  of  electricity  to 
common  matter,  we  find  the  following : — Some 
bodies  facilitate  the  transmission  of  electrical  action 
in  so  much  greater  degree  than  others,  that  they- 
have  been  considered  in  the  light  of  conductors  of 
electricity ;  other  bodies,  on  the  contrary,  admit  of 
so  little  freedom  in  this  respect  that  they  have  been 
denominated  non-conductors,  or  insulators  of  electri- 


8 


ELECTRICITY  CONSIDERED. 


city.  The  distinction,  however,  between  conductors 
and  non-conductors,  although  more  or  less  arbitrary, 
may  still  be  sufficiently  defined  for  practical  pur¬ 
poses  : — thus  all  the  metals  more  particularly  may 
be  taken  as  conducting  bodies,  whilst  all  vitreous 
and  resinous  substances  may  be  considered  as  non¬ 
conducting  bodies,  or  insulators.  Hence  it  is,  that 
we  find  the  metallic  conductors  opposed  to  the  cyl¬ 
inder  of  an  electrical  machine,  supported  on  a  glass 
pillar ;  by  which  the  active  electricity  developed  by 
the  friction,  becomes  as  it  were  imprisoned, — and 
accumulated  on  the  metal. 

It  should,  however,  be  clearly  understood,  that 
there  are  no  substances  which  perfectly  conduct  or 
'perfectly  obstruct  the  transmission  of  electricity,  their 
insulating  or  conducting  power  being  only  a  differ¬ 
ence  in  degree :  still  the  differences  are  so  great  be¬ 
tween  various  substances,  that  if  classed  in  relation 
to  such  differences,  those  at  the  extremes  of  the 
series  admit  of  being  considered,  the  one  as  conduc¬ 
tors,  the  other  as  insulators.  Thus,  while  vitreous 
and  resinous  bodies  admit  of  but  extremely  slow 
conduction,  during  which  sensible  and  even  consid- 
•  erable  portions  of  time  elapse,  metallic  bodies  allow 
conduction  to  proceed  with  incredible  rapidity.  Pro¬ 
fessor  Wheatstone,  by  a  highly  ingenious  experimen¬ 
tal  process,  has  clearly  shown,  that  the  transmission 
of  accumulated  electricity  through  a  copper  wire, 
one-fifteenth  of  an  inch  in  diameter,  and  about  half 
a  mile  in  length,  proceeds  at  the  rate  of  576,000 
miles  in  a  second  of  time ;  supposing  the  electrical 


IN  RELATION  TO  COMMON  MATTER. 


9 


action  to  move  from  one  extremity  to  the  other ;  and 
that  the  light  of  the  spark  produced  by  it,  has  a  less 
duration  than  the  one-millionth  part  of  a  second. 

The  learned  Mr.  Cavendish,  in  the  course  of 
some  extensive  inquiries  into  the  electricity  of  the 
torpedo,  found  the  difference  between  the  conducting 
powers  of  iron  and  water,  to  be  nearly  in  the  ratio 
of  four  hundred  millions  to  one ;  that  is  to  say,  elec¬ 
tricity  meets  with  no  more  resistance  in  passing 
through  an  iron  rod  four  hundred  millions  of  inches 
long,  than  it  would  meet  with  in  passing  through  a 
column  of  water  of  the  same  diameter,  only  one  inch 
long.* 

Table  showing  the  order  of  the  Conducting  and  Insu¬ 
lating  Powers  of  various  Substances. 


CONDUCTORS. 

INSULATORS. 

f  All  known  metals. 

r  Ice  at  0°  of  Fahrenheit. 

Well-burned  charcoal. 

Dried  vegetable  substance. 

Plumbago. 

o 

Dried  animal  substances. 

o--< 

Burning  gaseous  matter,  as  flame. 

>-< 

Parchment.  Leather.  Feathers. 

Smoke. 

Baked  wood. 

s 

.Concentrated  acids. 

OO 

a> 

Oils  and  fatty  substances. 
Bituminous  matter. 

c> 

'Dilute  acids. 

Saline  fluids. 

LSilk. 

Living  animals. 

r  Animal  fur  and  hair. 

Living  vegetables. 

Dry  gases,  including  the  atmos¬ 
phere. 

CQ 

Wood  in  its  ordinary  state. 

.  Snow  and  ice. 

•4^ 

CP 

*4-4 

Pure  steam  of  high  elasticity. 

Glass  and  all  vitrefactions. 

'  Aqueous  vapor. 

Diamond.  Transparent  gems. 

Common  earth  and  stone. 

QD 

Talc. 

Dry  chalk  and  lime. 

Amber. 

Marble  and  porcelain. 

All  resins  and  resinous  bodies. 

E 

Paper. 

.  Alkaline  matter. 

Brimstone. 

.  Shell-lac. 

*  Phil.  Trans,  for  1834,  Part  II. 


10 


ELECTRICITY  CONSIDERED 


If  we  arrange  various  kinds  of  substances  in 
series,  according  to  the  comparative  degree  of  resist¬ 
ance  they  offer  to  the  transmission  of  electricity,  we 
obtain  the  following  order.  The  first  column  in  the 
preceding  Table  contains  the  best  conductors,  and 
leads  by  degrees  into  the  second  column,  in  the 
order  of  their  increasing  resistance,  until  we  arrive 
at  the  opposite  extreme. 

The  order  above  given,  is  sufficiently  near  the 
truth :  it  is  almost  impracticable,  however,  to  assign 
the  exact  place  of  some  of  the  equivocal  substances, 
more  especially  as  their  conducting  power  is  liable 
to  vary  from  many  accidental  causes.  All  charcoal 
will  not  conduct  equally  well,  and  some  bodies  which 
conduct  badly  as  solids,  will,  by  a  change  of  temper¬ 
ature  up  to  fluidity,  become  immediately  conduc¬ 
tors  :  thus  ice  at  0°  of  Fahrenheit  is  an  insulator, 
but  on  approaching  the  melting  point  it  becomes  a 
conductor; — the  conducting  power  of  green  vegeta¬ 
bles,  and  raw  meat,  depends  on  the  fluids  they  con¬ 
tain.  The  extremes  of  the  series,  however,  are  per¬ 
fectly  defined ;  if  we  commence  with  the  metals  we 
have  the  order  of  conducting  power,  and  conversely, 
by  commencing  with  shell-lac,  we  have  the  order  of 
insulating  power. 

For  the  purpose  of  a  greater  degree  of  generali¬ 
zation,  we  may  include,  in  the  conducting  class,  all 
metals  and  metallic  ores,  acids,  saline  bodies,  all 
fluids  except  oils,  also  stones  and  earthy'matter,  liv¬ 
ing  animals  and  vegetables. 

Under  the  insulating  class,  we  may  comprise  all 


IN  RELATION  TO  COMMON  MATTER. 


11 


resinous  and  bituminous  matter,  all  vitreous  matter, 
all  gaseous  matter,  precious  stones,  dry  animal  and 
vegetable  matter,  silk  and  oils. 

The  following  is  an  easy  and  simple  experimental 
illustration  of  the  conducting  and  insulating  power 
of  various  bodies  in  respect  of  ordinary  electricity. 

Let  a  succession  of  sparks  about  two  inches  in 
length,  continue  to  pass  from  the  insulated  conductor 
of  an  electrical  machine  to  a  metallic  ball  in  connec¬ 
tion  with  the  ground.  Apply  now  a  stick  of  sealing- 
wax,  or  a  dry  rod  of  glass,  to  the  conductor,  no 
sensible  effect  will  be  produced  on  the  current  of 
sparks.  But  if  the  conductor  be  touched  with  a  rod 
of  wood,  or  put  into  communication  with  the  walls 
of  the  building,  the  sparks  will  immediately  cease, 
evidently  showing  that  the  accumulated  electricity 
had  been  by  these  last  substances  carried  off,  whilst 
the  wax  and  glass  evinced  no  such  power.  In  this 
way  we  may  test  the  conducting  power  of  the  vari¬ 
ous  substances  above  given,  either  directly,  or  by  in¬ 
closing  them  in  non-conducting  tubes. 

Although  the  distinction  between  conductors  and 
non-conductors  of  electricity  is  to  a  great  extent 
arbitrary,  yet  it  is  plain  from  the  above  facts,  that 
such  a  distinction,  in  a  positive  sense,  is  quite  ad¬ 
missible.  Thus  the  substances  commencing  the  first 
column  of  the  preceding  table,  may  be  taken  as 
being  more  especially  conductors ;  those  terminating 
the  second,  as  obstructors  or  non-conductors  of  elec¬ 
tricity  :  and  the  great  practical  fact  which  marks  the 
distinction  between  them  is  this, — that  the  substances 


12 


ELECTRICAL  CONDITIONS 


considered  more  especially  as  insulators,  oppose  such 
complete  resistance  to  the  transmission  of  electrical 
action,  that  an  instantaneous  return  of  the  disturb¬ 
ance  to  a  state  of  quiescence  (p.  4),  is  never  effected 
through  them,  without  mechanical  violence  and  dis¬ 
placement  of  their  particles,  without  a  vivid  evolu¬ 
tion  of  light  and  heat,  and  without  producing  at  the 
same  time,  all  the  furious  effects  peculiar  to  an 
irresistible  expansive  force.  The  best  conducting 
substances,  on  the  contrary,  yielding  as  they  do 
almost  immediately  to  the  electrical  transmission  (p.  8), 
at  once  quiet  the  disturbance  without  any  such  dis¬ 
astrous  consequences.  The  transmission  through 
these  is  comparatively  passive;  and  it  is  only  in 
some  few  instances  to  be  hereafter  considered,  that 
we  find  the  small  degree  of  resisting  power  they 
possess,  productive  of  any  ill  consequence,  and  then 
only  to  the  conducting  substance  itself,  not  to  neigh¬ 
boring  bodies. 

Electrical  conditions  of  a  Thunderstorm. 

We  are  indebted  to  Dr.  Faraday’s  valuable  and 
most  interesting  series  of  Inquiries  in  Electricity,* 
for  very  practical  and  sound  views  of  the  nature  of 
electrical  action.  These  we  shall  now  proceed  to 
apply  to  the  conditions  of  a  thunderstorm,  which 
will  serve  at  the  same  time  to  explain  them. 

A  thunderstorm  may  be  considered,  as  the  result 
of  a  great  electrical  disturbance  (pp.  4,  5),  between 


*  Phil.  Trans.  1881,  to  1838. 


OF  A  THUNDERSTORM. 


13 


masses  of  vapor  condensed  in  the  atmosphere  under 
the  form  of  clouds,  a  portion  of  the  earth’s  surface 
directly  opposed  to  these  masses,  and  the  inter¬ 
mediate  air ;  the  particles  of  which  instead  of  allow¬ 
ing  the  disturbance  to  subside  rapidly,  virtually 
maintain  it  up  to  a  point,  at  which  its  force  is  no 
longer  to  be  resisted.  For  example ;  let  the  mass 
of  vapor  p  p  (fig.  1),  under  the  form  of  a  cloud,  be 

Fig.  1. 


P 

o 

o 

o 

o 

_  N 

supposed  to  contain  active  electricity,  in  consequence 
of  some  of  those  changes  in  the  condition  of  the 
atmosphere,  to  which  we  have  already  alluded  (p.  5). 
Let  N  N  be  a  portion  of  the  earth’s  surface  directly 
opposed  to  these  masses ;  and  A  the  intermediate 
atmospheric  particles.  Now,  Faraday  has  shown, 
that  in  such  a  case  as  this,  all  these  intermediate 
particles  assume  a  peculiar  forced  electrical  state, 
which  he  terms  a  polarized  state.  By  way  of  typical 
illustration,  let  a,  5,  c  (fig.  2),  represent  three  of  these 
consecutive  particles,  and  suppose  in  their  neutral 
condition  the  electrical  distribution  of  each  particle 


14 


ELECTRICAL  CONDITIONS 


to  be  uniform  and  equal,  as  indicated  by  the  equali¬ 
zation  of  the  dark  and  light  squares.  Now,  when 
these  particles  become  placed  under  the  influence  of 
a  thunderstorm,  as  represented  in  figs.  1  and  4,  there 
would  be  no  longer  this  uniform  distributiom  The 
electricity  of  the  particles  would  be  compelled  to 


Fig.  2.  Fig.  3. 


assume  some  new  condition,  such,  for  example,  as 
that  shown  in  fig.  8 ;  that  is,  we  may  consider  the 
electrical  agency  as  being  no  longer  distributed 
according  to  a  law  of  quiescence,  but  to  be,  as  it 
were,  collected  in  the  particle  in  some  other  way, 
according  to  a  law  of  disturbance.  Suppose  this 
represented  by  the  shadowed  and  light  portions  of 
the  particles  a  h'  c  (fig.  8),  the  dense  portions  being 
constrained  to  appear  in  opposition  to  the  light  ones; 
and  let  us  further  imagine,  that  this  state  consists  in 
a  concentration  of  the  electricity  of  each  particle  in 
one  of  its  opposite  faces :  in  this  case  the  particles 
are  said  to  be  polarized. 


OF  A  THUNDERSTORM. 


15 


The  immediate  consequence  of  such  a  forced 
state  as  this,  is,  that  the  electrieitj,  rendered  active 
by  any  of  the  causes  above  mentioned  (p.  5),  propagates 
through  an  insulating  medium,  such  as  the  air,  a 
species  of  disturbance  from  particle  to  particle,  which 
at  last  arriving  at  distant  conducting  substances, 
elicits  an  active  electrical  condition  of  such  sub¬ 
stances,  similar  in  effect  to  the  primary  disturbance, 
but  opposite  in  kind.  This  Faraday  shows  to  *be  the 
essence  of  that  peculiar  action  of  electrified  on  distant 
bodies,  termed  induction.  Thus,  assuming  by  way 
of  illustration  that  P  (fig.  4)  were  a  cloud  containing 


Fig.  4. 


a  greater  quantity  of  electricity,  than  it  could  support 
in  a  state  of  quiescence,  there  would  be  immediately 


16 


ELECTRICAL  CONDITIONS 


propagated  througli  the  intermediate  particles  of  air 
a,  6,  c,  c?,  &c.,  an  induced  action  of  this  kind, — the 
intermediate  particles  a,  c,  c?,  would  be  constrained 
to  assume  the  polarized  state  just  mentioned.  There 
would  be,  according  to  the  principle  we  have  just 
supposed,  an  alternate  electrical  condensation  and  ex¬ 
haustion  P  7?,  p  77,,  7? 2?  brought* into  play,  which 

at  last  reaching  the  earth’s  surface,  would  there  elicit 
an  electrical  force,  N,  exactly  equal  to  the  force  at  p, 
but  of  an  opposite  or  neutralizing  quality;  so  that 
there  would  arise  at  N,  by  this  kind  of  action,  an 
electrical  exhaustion  or  displacement,  just  sufficient 
to  tranquillize  the  active  accumulation  at  p.  Now 
it  is  of  no  consequence  to  the  general  result,  which 
of  these  opposite  states  p,  n  be  supposed  to  reside  in 
the  cloud  p :  we  evidently  may  conceive  the  whole 
chain  (fig.  4)  to  exist  without  any  actual  change  in  its 
condition,  although  the  point  N  were  imagined  to  be 
the  state  of  the  cloud,  and  p  that  of  the  earth*:  the 
intermediate  particles  a,  c,  c?,  would  still  become 
polarized  in  the  same  way,  but  in  an  opposite  sense. 
We  have  only  to  conceive  the  figure  reversed,  and 
this  will  be  immediately  apparent,  the  conducting 
surfaces  of  the  clouds  and  earth,  being  nothing  more 
than  the  terminating  planes  of  a  great  intermediate 
action,  set  up  between  them  in  a  given  direction.* 
The  induced  disturbance  at  N,  in  the  points  im- 

*  Faraday  has  not  unaptly  termed  insulating  bodies  dielectrics, 
and  the  media,  through  which  induction  is  sustained,  dielectric 
media,  as  expressive  of  substances  through  which  electrical  action 
is  propagated  from  particle  to  particle. 


OF  A  THUNDERSTORM. 


11 


mediately  opposed  to  tlie  electrical  cloud  p,  may  be 
considered  as  a  species  of  reaction,  and  as  giving  ori¬ 
gin  to  a  new  force.  We  have,  therefore,  in  every 
disturbance  of  this  kind,  two  forces  present,  exactly 
equal  and  opposite  to  each  other.  These  opposite 
electrical  states,  have  been  imagined  by  some  philoso¬ 
phers,  to  depend  on  the  presence  of  two  equally 
powerful,  but  dissimilar  agents,  termed  the  vitreous 
and  resinous  electricities,  from  the  circumstance  of 
one  of  them  being  very  commonly  produced  by  the 
excitation  of  vitreous,  the  other  by  the  excitation  of 
resinous  substances.  There  is  not,  however,  any  es¬ 
sential  difference  between  them,  so  far  as  relates  to 
their  action  as  physical  forces ;  and  although,  for  the 
sake  of  perspicuity,  they  may  be  considered  as  posi¬ 
tive  and  negative  powers,  or  as  positive  and  negative 
electricities ;  jet  it  is  still  to  be  remembered,  that  one 
is  as  much  a  positive  force  as  the  other.  It  will  be 
immediately  perceived,  that  the  two  forces  must  ne¬ 
cessarily  exist  both  at  the  same  time  (p.  15)  as  at  P,  N 
(fig.  4) :  henee  it  is  found  impossible  to  charge  com¬ 
mon  matter  with  one  of  them,  without  the  other  ap¬ 
pearing  somewhere,  either  in  near  or  distant  bodies,* 
just  as  it  is  impossible  to  pull  against  a  fixed  point, 
without  eliciting  in  that  point,  an  equal  and  oppo¬ 
site  force. 

Insula tion —  Conduction —  G harge — Disch a rge^  &c. 

These  points  being  apprehended,  we  are  immedi¬ 
ately  prepared  to  receive  the  simple  and  lucid  expla- 

4 

*  Faraday’s  Researches  in  Electricity^  p.  865. 


18 


INSULATION - CONDUCTION - 


nation,  which  this  eminent  philosopher  has  given  ns, 
of  the  terms,  insulation,  conduction,  charge,  dis¬ 
charge,  &c. 

We  have  already  shown  (p.  15)  in  what  that  pecu¬ 
liar  and  wonderful  influence,  termed  electrical  induc¬ 
tion,  may  be  said  to  consist,  viz.,  a  polarization,  or 
forced  state  of  material  particles,  by  which  an  action 
is  propagated,  and  made  to  appear  in  bodies  however 
distant.  This  we  have  conventionally,  or  typically, 
represented  in  fig.  4,  page  15 ;  now  supposing  this 
state  of  the  particles  could  be  maintained  under  all 
circumstances,  complete  obstruction  to  the  return  of 
the  opposite  forces  to  a  state  of  quiescence  would  be 
the  result ;  and  we  should  arrive  at  perfect  insulation 
of  these  forces.  This  however  is  not  the  case,  the 
constrained  state  of  the  particles  will  not  remain,  ex¬ 
cept  for  a  limited  portion  of  time.  Thus  in  fig.  4, 
the  positive  force  in  p,  -will,  if  sufficient  time  be  al¬ 
lowed,  discharge  into  the  negative  force  n  of  particle 
n,  the  positive  force  of  this  particle  into  the  negative 
force  w,  of  particle  and  so  on  to  the  negative  force 
N,  until  the  whole  disturbance  is  quieted,  and  the  po¬ 
larization  of  the  particles  u,  c,  cf,  reduced.  This 
process  constitutes  conduction,  and  it  always  proceeds 
more  or  less  rapidly  through  every  kind  of  substance ; 
the  more  rapidly  however  it  can  proceed,  the  better 
the  conducting  power,  and  conversely,  the  less  freely 
it  can  proceed,  the  more  perfect  the  insulating  power 
(p.  7). 

.  Insulating  bodies  are,  therefore,  as  already  ob¬ 
served  (p.  8).  only  conductors  of  a  rigid  and  stubborn 


CHARGE - DISCHARGE,  ETC. 


19  - 


kind,  the  particles  of  which  return  to  their  normal 
state  so  slowly,  that  for  a  limited  portion  of  time, 
they  admit  of  being  considered  as  exceptions  to  the 
general  law  of  conduction  ;  yet  it  is  upon  these  bodies 
that  the  process  of  induction  depends,  and  upon  this 
process  depends  further,  the  state  of  things  called 
electrical  charge,  typically  illustrated  in  fig.  4.  As 
long  as  the  particles  a,  5,  c,  &c.,  can  suffer  the  con¬ 
strained  state  in  which  they  are  placed  (p.  12),  so  long 
will  the  charge  be  maintained  with  but  small  loss ; 
but  when  they  can  no  longer  resist  the  tendency  of 
the  opposite  electrical  forces  p,  N,  to  combine  through¬ 
out  the  series,  we  have  immediately  what  Faraday 
terms  disruptive  discharge — that  is  to  say,  the  parti¬ 
cles  in  fig.  1  (page  13),  are  displaced  and  broken 
through,  with  a  greater  or  less  degree  of  mechanical 
violence.  In  this  case,  the  electrical  disturbance  in 
the  particles  having  become  as  great  as  they  can  sus¬ 
tain,  any  tendency  to  further  disturbance,  instead  of 
inducing  further  change,  subverts  the  whole  system, 
and  a  violent  reunion  of  the  opposite  electrical  forces 
instantly  ensues. 

Although  such  discharges  are  of  a  sudden  and 
violent  character,  and  productive  of  damage  to  bodies 
through  which  they  pass,  yet  they  occasionally  be¬ 
come  so  modified  by  various  circumstances,  as  to  as¬ 
sume  a  more  progressive  and  quiet  form,  often  free 
from  any  attendant  danger  whatever. 

If  a  pointed  metallic  rod,  E  (fig.  5),  project  freely 
into  a  charged  system,  P,  E,  N,  from  one  of  its  termi¬ 
nating  planes  N,  the  polarized  particles  immediately 


20 


INSULATION - CONDUCTION - 


at  the  extremity  of  the  rod  have  the  forced  condition 
(p.  12)  so  highly  exalted,  that  it  terminates  in  discharge 
upon  the  next  or  more  remote  particles,  the  electrical 
condition  of  which  is  less  intense.  The  consequence 


Fio.  6. 


o  o  O  O  O 

o  o  O  o  O 


o  o  o  O  o 


of  this  is,  a  luminous  brush  of  beautifully  colored 
light,  attended  by  a  sort  of  roaring  noise.  This 
brush  discharge  may  be  considered  as  taking  place 
between  a  good  and  bad  conductor  :  it  is,  in  fact,  an 
intermitting  series  of  electrical  sparks  between  metal 
and  air ;  but  in  such  rapid  succession  as  to  convey 
the  idea  of  a  continuous  stream.  The  discharge  in 
this  case  always  commences  at  the  root  of  the  brush, 
and  is  complete  at  the  point  of  the  rod,  before  the 
more  distant  particles  attain  the  same  intensity: 
hence  the  discharge  is  progressive,  and  occupies  a 
sensible  time. 

Brush  discharge,  by  means  of  pointed  or  angular 


CHARGE - DISCHARGE,  ETC. 


21 


bodies,  will,  under  certain  conditions  of  conduction, 
assume  the  appearance  of  a  luminous  star,  especially 
when  it  is  proceeding  from  a  negative  or  resineus 
electricity  (pp.  16,  17).  Hence  the  observation,  that 
electrical  discharge  from  a  pointed  conductor,  is  at¬ 
tended  by  a  luminous  brush  of  rays,  but  toward  a 
pointed  conductor  by  a  star  of  light. 

When  the  air  in  contact  with  a  metallic  rod  is 
becoming  rapidly  charged,  we  have  another  species 
of  discharge,  termed  glow  discharge ;  that  is  to  say, 
the  metal  in  contact  with  the  electrified  particles  be¬ 
comes  covered  with  a  glow  of  lambent  light,  pro¬ 
ducing  a  beautiful  effect. 

Dr.  Watson,  in  the  48th  volume  of  the  Phil. 
Trans.^  has  collected  out  of  ancient  history  several 
interesting  notices  of  these  electrical  appearances. 
Thus  Pliny,  in  his  Natural  History^  tells  us  “  stars 
settled  on  the  sail-yards  and  masts  of  ships  with  an 
audible  sound :  also  on  the  spears  of  soldiers.” 
Seneca,  again,  in  his  Natural  Questions  says,  that  the 
“  spears  seemed  to  be  on  fire  in  the  Koman  camp.” 

Similar  appearances  are  mentioned  by  Caesar  and 
Livy. 

In  more  recent  periods,  we  find  repeated  notices 
of  similar  natural  phenomena.  They  are  called  by 
the  French  and  Spaniards,  St.  Helmo’s,  or  St.  Elmo’s 
fires ;  by  the  Italians,  the  fires  of  St.  Peter  and  St. 
Nicholas.  On  ship-board  in  this  country,  sailors 
call  them  comazants.  “In  the  night  (saj^s  the 
Count  de  Forbin)  we  saw  on  different  parts  of  the 
ship  above  thirty  St.  Helmo’s  fires ;  one  of  them  was 


22 


INSULATION - CONDUCTION - 


more  than  a  foot  and  a  half  in  height ;  its  noise  re¬ 
sembled  that  of  fired  gunpowder.”* 

Captain  Waddel,  of  the  meri^hant  ship  Dover ^  met 
with  a  heavy  electrical  storm  in  January,  1748 :  he  says, 
“Sundry  very  large  comazants  (as  we  call  them) 
settled  on  the  spindles,  and  burnt  like  very  large 
torches.”f  The  ship  was  soon  after  struck  by  light¬ 
ning.  Captain  Fanshawe,  R.  FT.,  observed  on  board 
his  Majesty’s  ship  Newcastle^  in  May,  1821,  luminous 
appearances  “  resembling  the  flame  of  a  gas-light 
on  the  extremities  of  the  masts  ;  the  lights  were  vi¬ 
sible  “  sometimes  on  one  mast,  sometimes  on  an¬ 
other,  and  sometimes  on  all  of  them.”  The  ship 
was  sailing  from  Bermuda  to  Halifax,  the  weather 
unsettled  and  squally,  with  a  “  mass  of  black  clouds 
close  astern,”  vivid  lightning  and  thunder  occa¬ 
sionally. 

At  Plauzet,  in  France,  the  three-pointed  extre¬ 
mities  of  the  cross  of  the  steeple,  always  appeared  sur¬ 
rounded  with  a  body  of  flame  during  great  storms 
of  lightning.f 

M.  Toscan,  the  librarian  of  natural  history  in 
the  Botanic  Gardens  in  Paris,  witnessed,  in  May, 
1803,  during  the  presence  of  heavy  black  clouds,  a 
vivid  glow  of  electrical  light  on  a  bent  iron  bar 
surrounding  a  wall  in  the  gardens  ;  it  gave  him  the 
idea  of  a  large  ball  of  fire  of  a  foot  in  diameter,  and 
lasted  eighteen  seconds.  This  glow  discharge  pre- 

*  Phil.  IVans.,  vol.  xlviii. 
f  Phil.  Trans.,  voL  xlvi.  p.  3. 

:j:  Priestley’s  History  of  Electricity,  p.  27  3. 


CHARGE - DISCHARGE - ETC. 


23 


ceded  a  heavy  stroke  of  lightning  on  the  house 
about  six  feet  distant.* 

The  fact  of  discharge  occurring  between  bad 
and  good  conductors,  in  such  way  as  to  produce  a 
spark,  leads  in  some  degree  to  an  explanation  of 
certain  electrical  explosions  observed  to  occur,  al¬ 
though  rarely,  in  an  apparently  serene  sky.  Thus 
his  Majesty’s  ship  Dictator  is  said  to  have  been  struck 
and  damaged  by  a  fire-ball  at  Martinique,  in  the 
year  1794,  during  fine  weather.  In  this  case  the 
surface  of  the  sea  may  have  discharged  upon  the 
nearest  particles  of  air,  which,  by  some  of  those 
changes  so  frequently  taking  place  in  the  atmo¬ 
sphere  had  become  polarized.  It  is  not  improbable, 
that  on  the  same  principle,  luminous  electrical  dis¬ 
charges  may  occur  between  particles  of  polarized 
air  in  different  states  of  intensity,  producing  those 
progressive  appearances  more  especially  called  me¬ 
teors.  These  have  all  the  characters  of  a  dense  elec¬ 
trical  discharge  propagated,  as  it  were,  from  particle 
to  particle  through  a  considerable  space ;  and  pro¬ 
bably  dragging  into  its  path,  light  vapors  and  in¬ 
flammable  matter  floating  in  the  atmosphere,  and 
increasing  by  their  intense  ignition  the  luminous 
and  highly  brilliant  appearance  which  such  meteors 
exhibit. 

Identity  of  common  Electricity  with  the  agency  of 

Lightning. 

The  years  1745  and  1746  mark  an  important 

*  Gilb.  Anna!:,  xiii.,  p.  484. 


24 


IDENTITY  OF  COMMON  ELECTRICITY 


era  in  the  history  of  physical  science.  Yon  Kleist, 
dean  of  the  Cathedral  of  Kamin,  and  some  Dutch 
philosophers  in  the  university  of  Leyden,  in  endea¬ 
voring  to  confine  electricity  within  the  limits  of  a 
small  phial,  discovered  a  method  of  accumulating  it 
on  glass  to  a  most  unprecedented  degree,  and  of 
'  subsequently  discharging  it  through  bodies,  in  such 
a  way  as  to  produce  the  most  powerful  and  aston¬ 
ishing  effects.  By  these  discharges  a  fearful  sen¬ 
sation  could  be  impressed  on  living  animals — even 
life  itself  destroyed ; — metallic  substances  could  be 
violently  heated,  fused,  and  ignited  ; — inflammable 
bodies  set  on  fire,  and  the  most  compact  substances 
scattered  in  pieces,  as  if  acted  on  by  a  violent  ex¬ 
pansive  force.  When,  therefore,  the  cause  of  light¬ 
ning  became  identified  with  that  of  ordinary  elec¬ 
tricity,  with  the  very  element,  as  it  were,  by  which 
such  effects  were  produced  ;  and  the  gigantic  attempt 
of  Franklin  (about  seven  years  afterwards)  actually 
to  draw  electricity  from  the  clouds,  and  appropriate 
it  in  a  similar  way  to  the  purpose  of  experiment, 
had  fully  succeeded, — then  it  was,  that  these  artifi- 
ficial  electrical  accumulations  and  discharges  ac¬ 
quired  a  more  than  ordinary  interest,  as  furnishing 
us  with  a  valuable  means  of  investigating  by  minor 
experiments,  tbe  laws  and  operations  of  the  great 
discharge  in  thunderstorms. 

The  identity  of  common  electricity  and  lightning, 
although  not  fully  verified  until  the  year  1762,  had 
nevertheless  been  long  suspected.  Mr.  Gray,  an 
English  electrician,  observes  {Phil.  Trans,  for  1785), 


WITH  THE  AGENCY  OF  LIGHTNING. 


25 


that  the  electric  fire  seems  to  be  of  the  same  nature 
with  that  of  thunder  and  lightning,”*  and  the  cele¬ 
brated  Abbd  ISTollet,  in  his  Lemons  de  Physique^  acutely 
describes  many  great  points  of  resemblance  between 
them.  If  any  one  (he  observes)  should  take  upon 
him  to  prove  from  a  well  connected  comparison  of 
phenomena,  that  thunder  is,  in  the  hands  of  nature, 
what  electricity  is  in  ours, — that  the  wonders  we  ex¬ 
hibit  at  our  pleasure  are  little  imitations  of  those 
great  effects  which  inspire  us  with  awe,  and  that  the 
whole  depends  upon  the  same  mechanism,  if  it  is  to 
be  demonstrated  that  a  cloud  prepared  by  the  action 
of  winds,  by  heat,  &c.,  is  an  electrized  body, — I  avow 
this  idea,  well  supported,  would  be  to  me  a  source 
of  great  delight.” 

At  length  Franklin  in  America,  and  several  phi¬ 
losophers  in  France,  conceived  the  grand  thought  of 
bringing  the  element  of  lightning  out  of  the  atmo¬ 
sphere,  by  means  of  pointed  conducting  bodies ;  and 
in  the  year  1752  electrical  sparks  were  drawn  from 
the  clouds.  Tired  of  waiting  for  the  erection  of  a 
spire  at  Philadelphia,  on  which  he  proposed  to  fix  a 
pointed  rod  of  iron,  the  American  philosopher  had 
recourse  to  a  common  kite,  as  affording  an  immedi¬ 
ate  and  ready  access  to  the  region  of  lightnings.  The 
kite  had  a  pointed  wire,  and  the  twine  which  held  it 
was  attached  to  an  insulating  eord  of  silk.  A  passing 
shower  opportunely  wetted  the  twine,  and  increased 

*  Dr.  Wall  also  observes,  Phil.  Trans.,  vol.  xxvi.,  that  the  crack¬ 
ling  sound  and  light  produced  by  the  excitation  of  amber  represents 
in  some  degree  thunder  and  lightning. 

2 


26 


IDENTITY  OF  COMMON  ELECTRICITY 


its  conducting  power, — at  the  same  moment  electrical 
sparks  were  drawn  from  a  key  hung  on  the  extrem¬ 
ity  of  the  kite-string. 

In  the  mean  time,  Dalibard  and  Delor,  both  zeal¬ 
ous  partisans  of  Franklin,  had  drawn  electrical  sparks 
from  the  clouds  at  Paris  and  in  its  vicinity,  by 
means  of  pointed  iron  rods,  forty  feet  in  length,  ele¬ 
vated  upon  some  of  the  highest  ground  they  could 
find ;  and  thus  was  verified  one  of  the  most  interest¬ 
ing  and  important  theories  to  be  found  in  the  history 
of  physics. 

Dr.  Franklin,  in  remarking  on  the  similarity  be¬ 
tween  common  electricity  and  lightning,  cautions  his 
readers  against  any  degree  of  disparity  of  effect  as 
an  argument  against  the  identity  of  these  powers. 
It  is  no  wonder,  he  says,  that  the  effects  of  the  one 
so  far  surpass  the  other.  “  If  two  gun-barrels,  when 
electrified,  will  strike  at  two  inches  distance,  and 
make  a  loud  report,  at  how  great  a  distance  may 
10,000  acres  of  electrified  cloud  strike,  and  how  loud 
must  be  that  crack?” 

The  great  points  of  coincidence  between  the  com¬ 
mon  electric  discharge  and  lightning  may  be  thus 
specified : — 

Flashes  of  lightning  are  frequently  waving  and 
crooked,  of  a  zig-zag  or  forked  appearance,  some¬ 
times  diffuse  and  colored — the  same  is  true  of  sparks 
drawn  from  the  ordinary  electrical  machine. 

Lightning  most  commonly  falls  on  elevated  or 
pointed  objects — the  same  is  true  of  electricity. 

Lightning  seizes  on  the  readiest  and  best  line  of 


WITH  THE  AGENCY  OF  LIGHTNING. 


27 


transit  in  its  course  to  the  earth — the  same  is  true  of 
the  common  electrical  discharge. 

Lightning  burns  up  various  kinds  of  matter — 
fuses  and  ignites  metallic  bodies — the  same  is  true 
of  the  electrical  discharge. 

Lightning  rends  brittle  substances,  and  scatters 
various  kinds  of  matter,  as  if  they  were  acted  on  by 
a  violent  expansive  force — such  is  also  the  case  with 
electricity. 

Lightning  impresses  on  living  animals  a  peculiar 
nervous  shock,  and  sometimes  destroys  life — this  is 
also  the  case  with  electricity. 

Lightning  reverses,  destroys,  or  gives  magnetic 
polarity  to  steel — such  is  also  the  result  of  powerful 
electrical'  discharges. 

When  these  coincidences  are  considered,  together 
with  the  fact  that  electricity  may  be  drawn  out  of 
the  clouds  and  air,  and  applied  to  produce  precisely 
the  same  effects  as  those  resulting  from  a  common 
electrical  machine,  it  becomes  quite  evident  that  the 
cause,  whatever  it  be,  of  ordinary  electrical  pheno¬ 
mena,  is  identical  with  that  of  lightning ;  conse¬ 
quently  we  arrive  at  the  important  deduction,  that 
common  electricity  and  lightning  are  subject  to  the 
same  laws, — a  deduction  which  cannot  be  too  forci¬ 
bly  insisted  on,  involving  as  it  does  the  most  valua¬ 
ble  practical  consequences. 

Nature  of  ordinary  Electidcal  Arrangements  producing 

Artificial  Lightning. 

The  great  discovery  of  the  electrical  jar,  to  which 


28 


ORDINARY  ELECTRICAL  ARRANGEMENTS 


we  have  adverted  (p.  23),  involves,  in  fact,  all  the 
conditions  of  a  thunderstorm,  the  disruptive  dis¬ 
charge  from  the  jar  being  the  same  in  effect  as  thun¬ 
der  and  lightning.  This  will  be  immediately  per¬ 
ceived  by  referring  to  what  has  been  already  ad¬ 
vanced  on  this  subject  (pp.  12,  15),  where  it  may 
be  seen  that  the  conditions  there  represented  are  re¬ 
ducible  to  the  separation  of  two  conducting  planes, 
p,  N  (fig.  1),  by  an  intermediate  insulating  substance 
A ;  one  of  the  conductors,  P,  being  limited,  the  other, 
N,  of  indefinite  extent.  Now,  to  complete  such  a 
system  artificially,  we  have  only  to  attach  two  con¬ 
ducting  surfaces,  P,  N  (fig.  6),  to  the  opposite  sides 
of  a  square  of  glass.  A,  B,  leaving  about  an  inch  of 


the  glass  clear  and  projecting  between  the  two.  If 
such  a  system  be  placed  on  a  conducting  base,  com¬ 
municating  with  the  earth,  it  is  evident  we  have  a 
limited  and  insulated  conductor,  p,  opposed  to  a  con¬ 
ductor,  N,  of  indefinite  extent.  Directly  we  charge 
this  system  on  the  insulated  surface,  P,  the  two  con¬ 
ducting  surfaces,  p  N,  become  the  terminating  planes 
of  a  great  electrical  action,  and  the  particles  of  the 
glass  become  polarized  by  induction  (p.  15) :  hence 
this  system  is  precisely  the  same  as  that  represented 
in  fig.  4.  The  nature  of  the  insulating  substance 


PRODUCINa  ARTIFICIAL  LIGHTNING.  29 

between  the  planes,  does  not  in  any  way  interfere 
with  the  conditions  of  this  arrangement,  nor  does  its 
thickness,  because  induction  goes  on  at  all  distances. 
Faraday  traced  it  from  a  small  electrified  ball  in 
the  middle  of  a  room  to  the  walls,  twenty-six  feet 
distant.*  It  takes  place,  however,  with  the  same 
constraining  force,  more  readily  according  as  the  ex¬ 
tent  of  the  intervening  insulation  is  lessened.  Hence 
it  is,  that  with  a  small  thickness  of  glass  we  obtain 
a  very  intense  action,  the  density  and  compactness 
of  the  glass  furnishing  a  resistance,  sufficient  to  main¬ 
tain  the  particles  in  their  polarized  condition.  This 
is  not  the  case  with  a  gaseous  insulation,  such  as  air, 
the  particles  of  which  soon  break  down  at  small 
distances,  under  the  reactive  force  of  the  opposite 
electrical  powers  (pp.  15,  19). 

It  is,  however,  requisite  here  to  understand,  that 
disruptive  discharges  from  this  arrangement  are  gen¬ 
erally  obtained  by  neutralizing  the  forces  through  a 
side  circuit  of  conductors  ;  that  is  to  say,  instead  of 


&  Fig.  7. 


allowing  the  intermediate  glass  to  become  broken 
down  by  the  force  between  the  conducting  planes,  P, 


*  Researches  in  Electricity,  p.  411. 


30 


ORDINARY  ELECTRICAL  ARRANGEMENTS 


N,  as  supposed  in  figs.  1  and  4,  we  discharge  the  sys¬ 
tem  through  a  side  circuit,  abode  (fig.  7).  This, 
however,  is  of  no  consequence  to  the  result  of  this 
experiment,  because  the  laws  of  such  discharges,  by 
which  the  system  is  reduced  to  electrical  quiescence, 
remain  the  same ;  and  any  substance  exposed  to  the 
effects  of  the  discharge  in  the  interval,  c,  would  be 
affected  in  precisely  the  same  way  as  if  it  were  in 
the  interval,  P,  N,  immediately  between  the  termina¬ 
ting  planes. 

Thus,  suppose  P  N  (fig.  8),  to  be  the  terminating 
planes  of  a  great  electrical  disturbance  in  an  interval 


Fig.  8. 


n 

P 

- - - — - 1 

1  ^ 

1 

1 

1 

1 

1 

a  ; 

- - 

P 

N 

of  air.  Imagine  a  conducting  path  suddenly  opened, 
and  the  system  discharged :  it  is  clear  that  whether 
such  a  path  were  opened  immediately  between  the 
planes  as  at  P  a  N,  or  at  the  edge  of  the  planes  as  at 
n  h  the  result  must  be  the  same.  Now,  imagine 
the  conducting  circuit  at  the  edge  of  the  planes  to 
be  curved  into  the  form  n  o  still  this  could  not 
possibly  affect  the  law  of  the  discharge  in  the  circuit, 
— but  this  last  is  the  case  in  question.  Suppose, 
further,  we  had  made  a  disruptive  interval  in  this 
discharging  conductor  in  any  point  of  it,  as  o,  a. 


PRODUCING  ARTIFICIAL  LIGHTNING. 


31 


still  tlie  result  of  tlie  discharge  in  sucb.  an  interval 
would  remain  invariable ;  consequently  we  may  as¬ 
sume  any  one  of  the  three  paths  of  discharge,  P  a  N, 
n  h  n  0  to  be  a  casual  association  of  bad  and 
good  conductors,  as  in  the  case  of  a  building,  with¬ 
out  in  any  way  afibcting  the  law  of  the  discharge 
through  them.  Therefore  let  the  immediate  position 
of  the  line  of  discharge  be  what  it  may,  whether 
immediately  between  the  planes  p,  n,  or  extending 
without  them  as  at  ii  o  5,  or  whether  interrupted  by 
a  large  interval  Y  a^nb^  n  still  the  laws  regulating 
the  neutralization  of  the  opposite  electrical  forces 
through  such  a  disjointed  circuit  must  be  always  the 
same. 

Then,  with  respect  to  the  immediate  mechanical 
form  or  arrangement  of  such  a  system,  that  is  also  a 
matter  of  indifference;  we  may  make  the  system 
cylindrical  if  we  please,  and  hence  the  immediate 
application  of  the  principle  to  the  Leyden  experi¬ 
ment  or  electrical  jar.  This  piece  of  electrical  appa¬ 
ratus  in  its  improved  state,  consists  of  two  conducting 
surfaces  P,  N  (fig.  9),  pasted  on  the  opposite  sides  of 
a  glass  jar,  a  portion  of  the  glass  d  d  being  left  clear 
and  projecting  between  them.  When  electricity  is 
communicated  to  the  interior  insulated  surface  P,  by 
means  of  a  rod  a  c,  the  outer  surface  N  resting  on  the 
ground,  the  whole  system  becomes  charged  as  in  the 
former  case,  and  may  hence  be  in  like  manner  dis¬ 
charged  by  means  of  a  curved  metallic  wire  b,  and 
if  we  connect  the  charging  rods  of  many  such  jars, 
all  resting  on  a  common  conducting  base,  we  may 


32 


ORDINARY  ELECTRICAL  ARRANGEMENTS 


charge  an(J  discharge  the  whole  together,  as  one 
great  system  of  enormous  power,  and  produce 
effects  approaching  to  those  of  lightning.  With  the 
great  battery  in  the  Tylerian  Museum  at  Haerlem, 
which  exposed  225  square  feet  of  insulated  metallic 
surface  d,  Yan  Marum  gave  polarity  to  stee^  bars  nine 


Fig.  9. 
a  b 


inches  long,  nearly  half  an  inch  wide,  and  one-twelffh 
of  an  inch  thick.  A  piece  of  box-wood  four  inches 
in  diameter  and  four  inches  in  length  was  rent  by  it 
in  pieces.  It  melted  readily  various  metals,  and  dis¬ 
persed  them  in  all  directions.  An  iron  wire  twenty- 
five  feet  long,  and  about  iloth  of  an  inch  in  diameter, 
fell  under  the  shock,  into  red  hot  balls  dispersing  in 
all  directions.  A  piece  of  tin  wire  eight  inches  long, 
and  one-eighteenth  of  an  inch  in  diameter,  disappear¬ 
ed  in  a  cloud  of  blue  smoke,  throwing  down  red-hot 
globules  of  tin,  which  repeatedly  rebounded  from  a 


PRODUCING  ARTIFICIAL  LIGHTNING.  33 

piece  of  paper  beneath  it.*  In  the  course  of  similar 
experiments  by  Mr.  Brook,  he  says,  “the  report  was 
so  very  loud,  that  our  ears  were  stunned,  and  the 
flash  of  light  so  very  great,  that  my  sight  was  quite 
confused  for  a  few  seconds.” 

The  electrical  machine  employed  by  Yan  Marum 
consisted  of  two  circular  plates  of  glass,  each  five 
feet  five  inches  in  diameter :  these  were  set  on  the 
same  axis,  and  were  rendered  electrical  by  revolving 
with  friction  between  eight  cushions,  each  about 
fifteen  inches  long,  and  two  inches  wide.  The 
power  of  this  splendid  instrument  was  such,  that 
bodies  at  forty  feet  distance  were  sensibly  influenced ; 
pointed  wires  became  tipped  with  a  star  of  light 
at  twenty -eight  feet  distance  (p.  19),  and  a  powerful 
current  of  brilliant  light  two  feet  or  more  in  length, 
crooked,  and  darting  forth  luminous  brushes  into  the 
air,  was  obtained  by  presenting  a  metallic  ball  in  con¬ 
nection  with  the  earth,  to  its  great  conductor.  A 
single  spark  melted  a  considerable  length  of  gold- 
leaf,  and  fired  various  kinds  of  combustibles. 

We  have  thought  it  not  unimportant  to  notice 
these  results,  as  having  a  direct  bearing  on  the  great 
question  of  the  defence  of  buildings  from  lightning. 
For  since  the  accumulation  of  electricity  by  artificial 
means  may  be  carried  to  an  almost  indefinite  extent, 
and  is  equally  manageable,  whatever  may  be  the 
extreme  limit  of  force  we  choose  to  assign  to  such 
accumulation, — it  necessarily  follows  that  discharges 


*  Roz.  xxxiii.  and  Phil.  Mag.,  vol.  viii. ;  Nich.  ii.  627. 
2^ 


34 


VARIOUS  PHENOMENA  OF 


of  atmospheric  electricity  may  be  quite  as  easily 
directed,  by  a  judicious  and  scientific  arrangement 
of  conducting  bodies  ;  such  discharges  being  in  fact, 
nothing  more  than  the  same  force  also  resulting  from 
a  species  of  electrical  machine,  and  accumulated  in  a 
similar  way,  by  means  of  an  apparatus  of  a  perfectly 
similar  kind.  The  vapory  masses  of  the  clouds, 
opposed  through  the  intermediate  air  to  the  surface 
of  ground  or  sea,  constitute  a  battery  of  enormous 
power.  The  circumstance  of  the  coatings  of  the  jar 
being  metallic,  whilst  those  in  nature  consist  of 
water,  is  a  difference  of  no  moment  whatever ;  espe¬ 
cially  when  we  consider  that  the  original  experiment 
of  the  Dutch  philosophers,  consisted  in  the  electrifi¬ 
cation  of  water  inclosed  in  a  small  phial,  from  which 
they  obtained  so  great  a  shock,  as  to  induce  one  of 
them  to  say  that  he  would  not  again  receive  it  for 
the  whole  kingdom  of  France. 

Yarious  Phenomena  of  Lightning  and  Thunder. 

The  identity  of  ordinary  electrical  discharges  with 
the  phenomena  of  thunder  and  lightning  being  thus 
satisfactorily  shown,  we  have  now  merely  to  consider 
some  of  those  modifications  of  the  effect,  characteristic 
of  these  great  natural  operations.  In  the  first  place, 
it  is  to  be  observed,  that  when  the  discharge  takes 
place  very  close  to  the  observer,  the  effect  is  a  brilliant 
vivid  light  of  momentary  duration,  intolerable  to  the 
eye,  and  attended  by  a  terrific  and  sudden  whizzing 
crash,  as  if  ten  thousand  porcelain  jars  had  fallen  on 
a  stone  pavement,  and  were  smashed  in  pieces. 


LIGHTNING  AND  THUNDER. 


35 


When,  however,  some  considerable  distance  is  inter¬ 
posed,  the  light  is  more  tolerable,  and  precedes  the 
crash  by  a  sensible  time ;  in  this  case  the  noise  begins 
to  soften  down  into  a  sort  of  reverberating  roar ;  at 
still  greater  distances  the  reverberations  are  taken 
up,  and  bandied  about  between  the  irregular  forms 
of  the  distant  clouds  and  the  surface  of  the  earth,  pro¬ 
ducing  what  has  been  termed,  in  common  language, 
peals  of  thunder.  A  similar  effect  ensues  on  the 
earth’s  surface,  during  the  discharge  of  cannon,  where 
surrounding  objects  present  irregular  sources  of  re¬ 
verberation:  on  the  sea,  where  so  few  obstacles  to 
the  diffusion  of  sound  exist,  distant  thunder  regular¬ 
ly  dies  away  in  a  sort  of  sullen  silence.  The  distance 
of  the  point  of  discharge,  may  be  estimated  by  the 
time  which  elapses  between  the  flash  of  lightning 
and  the  thunder ;  since  for  small  distances,  the  pro¬ 
gress  of  light  may  be  taken  as  instantaneous :  sound, 
on  the  contrary,  has  a  more  sensible  duration,  being 
propagated  through  the  air,  at  the  rate  of  eleven 
hundred  feet  in  a  second.  It  may  be  here  remarked, 
that  an  essential  distinction  exists  between  the  light  of 
lightning,  for  which,  as  Franklin  observes,  we  want 
an  appropriate  term,  and  the  presence  of  the  electrical 
agency  itself. 

Arago  divides  the  phenomena  of  lightning  into 
three  classes^^  In  the  first  he  places  those  luminous 
discharges  characterized  by  a  long  streak  of  light, 
very  thin,  and  well  defined  at  the  edges:  they  are 
not  always  white,  but  are  sometimes  of  a  violet,  or 
purple  hue;  they  do  not  move  in  a  straight  line, 


36 


VARIOUS  PHENOMENA  OF 


but  have  a  deviating  track  of  a  zig-zag  form.  They 
frequently  divide  in  striking  terrestrial  objects,  into 
two  or  more  distinct  streams,  but  invariably  proceed 
from  a  single  point.  The  Abbe  Eichard  witnessed 
a  discharge  of  this  kind  descend  from  a  cloud,  and 
divide  upon  two  separate  objects  on  coming  near  the 
earth.*  We  have  instances,  in  the  damage  done  to 
our  shipping,  of  the  trifurcation  of  lightning,  in 
which  the  three  masts  of  a  ship  have  all  been  struck 
by  the  same  discharge.  This  result  ensued  in  His 
Majesty’s  ship  Implacable^  under  the  command  of  Sir 
George  Cockburn,  in  July,  1810,  near  the  Isle  of 
Wight.  The  fore  and  mizzen  topgallant-masts  were 
shivered,  and  traces  of  the  discharge  were  left  on  the 
main-mast. 

Under  the  second  class,  Arago  has  placed  those 
luminous  effects  not  having  any  apparent  depth,  but 
expanding  over  a  vast  surface :  they  are  frequently 
colored  red,  blue,  and  violet;  they  have  not  the 
activity  of  the  former  class,  and  are  generally  con¬ 
fined  to  the  edges  of  the  cloud  from  which  they 
appear  to  proceed. 

The  third  class  comprises  those  more  concentrat¬ 
ed  masses  of  light,  which  he  has  termed  globular 
lightning.  The  long  zig-zag  and  expanded  flashes, 
exist  but  for  a  moment,  but  these  seem  to  endure 
for  many  seconds :  they  appear  to  occupy  time,  and 
to  have  a  progressive  motion. 

It  is  more  than  probable,  that  many  of  these 


*  Histoire  Naturelle  de  V Air  et  des  Ifetiores. 


LIGHTNING  AND  THUNDER. 


37 


phenomena  are  at  least  reducible  to  the  common 
progress  of  the  disruptive  discharge,  modified  by  the 
quantity  of  passing  electricity,  the  density  and  con¬ 
dition  of  the  air,  and  the  brilliancy  of  the  attendant 
light.  When  the  state  of  the  atmosphere  is  such, 
that  a  moderately  intense  discharge  can  proceed  in 
an  occasionally  deviating  zig-zag  line,  the  great  nu¬ 
cleus,  or  head  of  the  discharge,  becomes  drawn  out 
as  it  were,  into  a  line  of  light  visible  through  the 
whole  track ;  and  if  the  discharge  divides  on  ap¬ 
proaching  a  terrestrial  object,  we  have  what  sailors 
call  forked  lightning.  If  it  does  not  divide,  but  ex¬ 
hibits  a  long  rippling  line,  with  but  little  deviation, 
then  they  call  it  chain  lightning.  What  sailors  term 
sheet  lightning,  is  the  light  of  a  vivid  discharge  re¬ 
flected  from  the  surfaces  of  distant  clouds,  the  spark 
itself  being  concealed  by  a  dense  intermediate  mass 
of  cloud,  behind  which  the  discharge  has  taken 
place.  In  this  way  an  extensive  range  of  cloud  may 
appear  in  a  blaze  of  light,  producing  a  truly  sublime 
effect.  The  appearance  termed  globular  lightning, 
may  be  the  result  of  similar  discharges ;  it  is  no 
doubt  always  attended  by  a  diffusely  luminous  track, 
this  may,  however,  be  completely  eclipsed  in  the 
mind  of  the  observer,  by  the  great  concentration  and 
density  of  the  discharge,  in.  the  points  immediately 
through  which  it  continues  to  force  its  way,  and 
where  the  condensation  of  the  air  immediately  be¬ 
fore  it  is  often  extremely  great.  It  is  this  intensely 
illuminated  point  which  gives  the  notion  of  globular 
discharge ;  and  it  is  clear,  from  the  circumference  of 


38  APPEARANCES  TERMED  FIRE-BALLS. 

air  which  may  become  illuminated,  the  apparent 
diameter  will  be  often  great.  Mr.  Hearder,  of  Ply¬ 
mouth,  once  witnessed  a  discharge  of  lightning  of 
this  kind  on  the  Dartmoor  hills,  very  near  him. 
Several  vivid  flashes  had  occurred,  before  the  mass 
of  clouds  approached  the  hill  on  which  he  was  stand¬ 
ing  :  before  he  had  time  to  retreat  from  his  danger¬ 
ous  position,  a  tremendous  crash  and  explosion  burst 
close  to  him.  To  use  his  own  words,  “  the  spark  had 
the  appearance  of  a  nucleus  of  intensely  ignited  mat¬ 
ter,  followed  by  a  flood  of  light ;  it  struck  the  path 
near  me,  and  dashed  with  fearful  brilliancy  down  its 
whole  length,  to  a  rivulet  at  the  foot  of  the  hill, 
where  it  terminated.” 

Appearances  termed  Fire-Balls. 

A  great  deal  has  been  said  relative  to  these  ap¬ 
pearances,  and  some  doubts  have  been  entertained 
of  their  real  existence  as  mere  balls  of  electrical 
light.  Nevertheless  the  evidence  of  the  existence 
of  a  form  of  disruptive  discharge,  faithfuly  convey¬ 
ing  to  the  observer  such  an  impression,  is  beyond 
question.  A  curious  instance  is  given  by  Mr.  Chal¬ 
mers  whilst  on  board  the  Montague^  of  seventy-four 
guns,  bearing  the  flag  of  Admiral  Chambers.  In 
the  account  read  at  theKoyal  Society,*  he  states  that 
“November  4th,  1749,  whilst  taking  an  observation 
on  the  quarterdeck,  one  of  the  quartermasters  re¬ 
quested  him  to  look  to%indward ;  upon  which  he 


*  Phil.  Trans.,  vol.  xlvi.,  p.  366. 


APPEARANCES  TERMED  FIRE-BALLS.  39 

observed  a  large  ball  of  blue  fire  rolling  along  on 
the  surface  of  the  water,  as  big  as  a  mill-stone,  at 
about  three  miles  distance.  Before  they  could  raise 
the  main-tack,  the  ball  had  reached  within  forty 
yards  of  the  main-chains,  when  it  rose  perpendicu¬ 
larly  with  a  fearful  explosion,  and  shattered  the  main- 
topmast  in  pieces.”  In  an  account  of  the  fatal  ef¬ 
fects  of  lightning,  in  June,  1826,  on  the  Malvern 
Hills,  when  two  young  ladies  were  struck  dead,  it  is 
stated  that  the  electric  discharge  “  appeared  as  a 
mass  of  fire  rolling  along  the  hill  towards  the  build¬ 
ing  in  which  the  party  had  taken  shelter.”* 

The  great  number  of  accounts  of  such  appear¬ 
ances,  and  the  remarkable  coincidences  in  them  all, 
extending  as  they  do  through  nearly  a  whole  cen¬ 
tury,  and  consequently  given  by  observers  in  no  way 
connected  with  each  other,  leave  not  the  least  doubt 
of  their  existence.  M.  Deslandes  transmitted  to  the 
Academy  of  Science  in  Paris  an  account  of  a  terrible 
thunderstorm  in  Brittany,  in  April  1718,  which 
completely  destroyed  a  church  near  Brest.  In  this 
account  it  is  stated  that  the  damage  was  done  by 
three  large  globes  of  fire  of  three  feet  and  a  half  in 
diameter,  which  fell  at  once  on  the  spire.f 

It  is  by  no  means  easy  to  explain  these  appear¬ 
ances  on  the  principles  applicable  to  the  ordinary 
electric  spark :  the  amazing  rapidity  with  which  this 
proceeds,  and  the  momentary  duration  of  the  light 


*  Loyds  Evening  Post. 

\  Annuaire  pour  1838,  p.  259. 


40 


APPEARANCES  TERMED  FIRE-BALLS. 


(p.  8),  renders  it  almost  a  matter  of  impossibility  that 
the  discharge  should  appear  under  the  form  of  a  ball 
of  fire ;  it  would  be  a  transient  line  of  light :  we  must 
look,  therefore,  to  some  other  source  for  an  explana¬ 
tion  of  these  appearances. 

Now  it  is  not  improbable,  that  in  many  cases  in 
which  distinct  balls  of  fire  of  sensible  duration  have 
been  perceived,  the  appearance  has  resulted  from  the 
species  of  brush  or  glow  discharge  already  described 
(p.  19),  and  which  may  often  precede  the  main 
shock :  the  ball  of  fire,  observed  by  M.  Toscan  at 
the  Botanic  Grardens  in  Paris,  was  evidently  a  result 
of  this  kind.  In  short,  it  is  not  difficult  to  conceive, 
that  before  a  discharge  of  the  whole  system  takes 
place,  that  is  to  say,  before  the  constrained  condition 
of  the  dielectric  particles  of  air  intermediate  between 
the  clouds  and  earth  (p.  15)  becomes  as  it  were  over¬ 
turned,  the  particles  nearest  one  of  the  terminating 
planes,  or  other  bodies  situate  on  them,  may  begin 
to  discharge  upon  the  succeeding  particles,  and  make 
an  effort  to  restore  the  neutral  condition  of  the  sys¬ 
tem  by  a  gradual  process.  Such  was  doubtless  the 
case  in  the  instances  given  by  M.  Deslandes  and  M. 
Toscan. 

If  therefore  we  conceive  the  discharging  particles 
to  have  progressive  motion  from  any  cause,  then  we 
shall  immediately  obtain  such  a  result  as  that  ob¬ 
served  by  Mr.  Chalmers  on  board  the  Montague  (p. 
88),  in  which  a  large  ball  of  blue  fire  was  observed 
rolling  on  the  surface  of  the  water,  towards  the  ship 


APPEARANCES  TERMED  FIRE-BALLS. 


41 


from  to  windward.  This  was  evidently  a  sort  of  glow 
discharge,  or  St.  Helmo’s  fire,  produced  by  some  of 
the  polarized  atmospheric  particles  yielding  up  their 
electricity  to  the  surface  of  the  water,  much  in  the 
same  way,  as,  in  the  appearance  observed  by  M.  Tos- 
can,  the  stationary  cloud  did  on  the  land.  The 
clouds,  however,  were  here  in  rapid  motion,  the 
ship  at  the  time  being  under  topsails  and  courses 
only,  in  consequence  of  the  strength  of  the  wind : 
the  discharging  particles,  therefore,  had  motion  to¬ 
wards  the  ship,  the  rate  of  which  appears,  from  the 
account  to  correspond  with  the  velocity  of  the  breeze. 
On  nearing  the  ship,  the  point  of  discharge  became 
transferred  to  the  head  of  the  mast ;  and  the  striking 
distance  being  thus  diminished,  the  whole  system  re¬ 
turned  to  its  normal  state  (p.  12),  that  is  to  say,  a 
disruptive  discharge  ensued  between  the  sea  and  the 
clouds  (p.  15),  producing  the  usual  phenomena  of 
thunder  and  lightning,  termed  by  the  observers,  the 
“rising  of  the  ball  through  the  mast  of  the  ship.” 
The  fatal  occurrence  on  the  Malvern  Hills  (p.  39)  is 
another  instance  of  the  same  kind.  A  similar  effect 
is  described  in  the  Phil.  Trans,  for  1773,  in  which  a 
ball  of  light  appeared  in  the  parlor  of  a  house  struck 
by  lightning  at  Steeple  Ashton.  The  ball  is  de¬ 
scribed  as  being  of  “the  size  of  a  sixpenny  loaf,  and 
surrounded  with  a  dark  smoke,”  and  is  said  “  to  have 
burst  with  a  loud  noise.”  This  too  was  evidently  a 
species  of  brush  or  glow  discharge  (p.  21),  preceding 
the  stroke  of  lightning  which  damaged  the  house. 

It  is  therefore  highly  probable,  that  all  these  ap- 


42 


SULPHUROUS  ODOR  OF 


pearances  so  decidedly  marked  as  concentrated  balls 
of  fire,  are  produced  by  tlie  glow  or  brush  discharge 
producing  a  St.  Helmo’s  fire  in  a  given  point  or 
points  of  the  charged  system  (p.  15),  previously  to 
the  more  general  and  rapid  union  of  the  electrical 
forces;  whilst  the  greater  number  of  discharges  de¬ 
scribed  as  globular  lightning,  are,  as  already  ob¬ 
served,  most  probably  nothing  more  than  a  vivid 
and  dense  electrical  spark  in  the  act  of  breaking 
through  the  air, — which,  coming  suddenly  on  the 
eye,  and  again  vanishing  in  an  extremely  small  por¬ 
tion  of  time,  has  been  designated  a  ball  of  light. 
Thus  in  a  thunderstorm  which  damaged  a  house  at 
Eastbourne,  in  Sussex,  in  September  1781,  balls  of 
fire  were  said  to  dart  from  the  clouds  into  the  sea. 
These  were  evidently  common  electrical  sparks  seen 
at  a  distance  ;  for  when  the  lightning  struck  the 
house,  “  multitudes  saw  the  meteor  dart  in  a  right 
line  over  their  heads,  and  all  agreed  that  the  form 
and  flame  were  exactly  like  that  of  an  immense  sky¬ 
rocket.”  * 

Sulphurous  Odor  of  the  Electric  Discharge. 

There  is  one  circumstance  noticed  by  the  cele¬ 
brated  Italian  philosopher,  Beccaria,  which  must  not 
be  lost  sight  of,  as  having  doubtless  great  influence 
over  these  appearances,  viz.,  the  tendency  of  the 
electrical  discharge  to  drag  into  its  path  light  con¬ 
ducting  substances,  which  can  facilitate  its  progress, 


*  Phil.  Trans,  for  1781,  p.  42. 


THE  ELECTRIC  DISCHARGE. 


43 


and  by  wliicli  it  is  enabled  to  strike  throngh  dis¬ 
tances  considerably  greater  than  would  otherwise  be 
traversed.  Thus  traces  of  smoke,  free  vapor,  or  any 
other  conducting  matter  floating  in  the  air,  will  fre¬ 
quently  determine  the  course  of  lightning,  and  not 
only  determine  it  as  to  direction,  but  greatly  modify 
its  appearance.  A  heated  or  whirling  column  of  air, 
such  as  is  sometimes  seen  to  arise  even  in  a  tranquil 
state  of  the  weather,  would  produce  a  similar  effect 
through  its  interior  and  rarefied  portion  ;  and  there 
is  little  doubt  that  conducting  matter,  when  dragged 
into  the  path  of  lightning,  would  be  intensely  heated 
and  decomposed.  Beccaria  once  received  an  electric 
shock  through  the  fumes  of  nitric  acid,  which  be¬ 
came  concentrated  and  driven  into  his  thumb  pro¬ 
ducing  a  small  round  hole ;  and  Priestley  found  that 
a  discharge  could  be  produced,  by  the  dispersion  of 
a  drop  of  water  which  hung  on  a  brass  rod  commu¬ 
nicating  with  the  inside  of  his  battery. 

The  transfer  and  ignition  of  ponderable  matter 
through  the  track  of  electrical  discharge,  may  be  ad¬ 
duced  to  explain,  in  some  degree,  the  suffocating  sul¬ 
phurous  odor  so  frequently  observed  at  the  time  of 
heavy  strokes  of  lightning :  on  ship-board  more  es¬ 
pecially,  when  great  damage  has  arisen,  and  the  elec¬ 
trical  discharge  has  exploded  below  decks,  this  sul¬ 
phurous  smell  is  described  as  quite  suffocating.  In 
the  case  of  the  Montague^  just  cited  (p.  38),  it  is  said 
of  this  odor,  that  “  the  ship  seemed  to  be  nothing 
but  sulphur.”  From  whence  this  arises  is  still  an 
interesting  problem  in  physics.  There  are  many 


44 


ARTIFICIAL  DISRUPTIVE  DISCHARGES. 


facts,  which  favor  the  idea  of  various  kinds  of  matter 
being  dragged  and  transported  into  the  track  of  the 
electrical  discharge,  either  immediately  from  the 
body  of  the  earth,  or  from  the  atmosphere  in  which 
they  are  often  found ;  and  it  is  not  impossible  in  this 
way  to  explain  those  apparently  solid  balls  of  fire 
termed  more  especially  meteors;  that  vapors  of  va¬ 
rious  kinds  may  greatly  modify  and  direct  disruptive 
discharge,  is  unquestionable,  and  hence  give  rise  to 
those  long,  truncated  appearances  of  fiame  frequently 
observed  in  discharges  of  lightning.  It  would  be 
trespassing  on  the  limits  of  this  work,  to  enter  at 
length  upon  the  theory  of  meteors,  or  upon  those 
chemical  views  which  some  able  philosophers  have 
entertained,  of  the  nature  of  the  odor  emitted  by  the 
electrical  discharge;  it  may  perhaps  be  suificient  for 
our  present  purpose  to  keep  it  in  view,  without  an 
elaborate  detail  of  its  possible  causes.* 

Artificial  Disruptive  Discharges, 

The  luminous  appearances  observable  in  the  great 
and  terrible  discharges  of  lightning,  may  be  com¬ 
pletely  obtained  by  artificial  means,  giving  rise  to 


*  Mr.  Benjamin  Cook,  F.  R.  S.,  states,  that  after  a  night  of  vivid 
lightning,  with  thunder,  an  oblong  ball,  of  a  bright  yellow  color, 
and  frosted  over  with  fine  yellow  crystals,  was  found  in  a  meadow 
far  from  any  house,  and  in  a  perfectly  undisturbed  surface  of  ground. 
The  ball  appeared  quite  fresh.  The  crystals  were  easily  displaced, 
and  the  matter  of  the  ball  was  principally  sulphur.  It  burned  with 
mild  sulphurous  flames. — Phil.  Trans.,  vol.  xl. 


ARTIFICIAL  DISRUPTIVE  DISCHARGES. 


46 


experiments  of  a  tigUy  instructive  kind.  The  con¬ 
ditions  which  modify  the  extent  and  appearance  of 
the  electrical  discharge,  produced  artificially,  are  the 
form  and  extent  of  the  conductors — ^between  which 
the  disturbance  has  taken  place,  the  quantity  of  ac¬ 
cumulated  electricity,  the  intensity  of  the  charge, 
and  the  nature  and  density  of  the  medium  through 
which  it  forces  its  way.  Between  round  and  even 
surfaces,  of  considerable  extent  as  compared  with  the 
♦  amount  of  electricity  accumulated,  the  sparks,  under 
common  states  of  the  air,  are  short  and  dense,  ap¬ 
proaching  in  appearance  globular  lightning:  and 
this  is  true  in  respect  of  electricity  passing  between 
any  two  parallel  surfaces,  and  is  even  applicable  to 
the  conditions  of  the  discharge  of  the  electrical  jar. 
The  opposed  conductors  P  N  (fig.  7),  so  influence  the 
form,  appearance,  and  dimensions  of  the  spark,  that 
we  cannot  obtain  under  common  circumstances, 
through  the  neutralizing  circuit  ah  cde,  a  more  ex¬ 
tensive  discharge  than  could  take  place,  supposing  it 
to  have  occurred  immediately  between  P  N,  the  ter¬ 
minating  planes  themselves.  Short  dense  discharges 
are  in  each  case  produced,  approaching  in  appearance 
to  many  of  those  in  nature,  called  by  sailors,  fire¬ 
balls. 

By  changing  the  disposition  and  form  of  the 
-  conductors,  we  obtain  longer  and  more  diffuse 
sparks,  of  a  zig-zag  and  waving  character,  which 
frequently  bifurcate,  and  otherwise  divide,  pro¬ 
ducing  appearances  similar  to  those  termed  by  mari¬ 
ners,  forked  and  chain  lightning.  All  this  greatly 


46 


ARTIFICIAL  DISRUPTIVE  DISCHARGES. 


depends  on  the  activity  of  the  charge,  which  again 
varies  with  the  extent  of  surface  upon  which  it 
passes;  the  activity  of  electricity  disposed  on  sur¬ 
faces  varying  in  dimensions,  being  in  an  inverse 
duplicate  ratio  of  the  surface,  the  quantity  being 
constant;*  that  is  to  say,  a  given  quantity  of  elec¬ 
tricity  collected  on  a  double  extent  of  conducting 
surface,  has  only  one-fourth  the  activity — on  a  treble 
extent  only  one-ninth — and  so  on.  Hence  an  elec¬ 
trical  disturbance  which,  between  terminating  planes 
of  large  dimensions,  would  be  comparatively  quies¬ 
cent,  becomes  active  and  unruly  between  planes  of 
much  less  extent.  When  large  quantities  of  elec¬ 
tricity,  therefore,  press  upon  small  .surfaces,  the 
spark  is  elongated  and  spiteful  in  its  character;  and 
if  these  be  indefinitely  reduced  to  mere  points,  the 
discharge  is  narrowed  into  a  sort  of  stream,  causing 
a  rapid  escape  of  the  electricity  under  such  -an  at¬ 
tenuated  form,  as  to  produce  a  comparatively  tran¬ 
quil  and  gradual  discharge  (p.  19).  It  is,  as  observed 
by  Faraday,  when  treating  of  this  curious  action  of 
pointed  conductors,  at  the  extremity  of  a  point,  that 
the  intensity  necessary  to  charge  the  air  is  first  ac¬ 
quired;  from  thence  the  particles  recede.  At  the 
same  time,  the  point,  having  become  the  origin  of 
an  active  mechanical  force,  does,  by  the  very  act  of 
causing  that  force,  namely,  by  discharge,  prevent 
any  other  part  of  the  conducting  body  from  which 
it  projects,  from  acquiring  the  same  condition,  and 
thus  preserves  its  own  predominance.  In  this  way 

*  Phil.  Trans,  for  1834,  p.  221. 


ARTIFICIAL  DISRUPTIVE  DISCHARGES. 


47 


pointed  conductors  operate  in  discharging  large  ac¬ 
cumulations  at  considerable  distances,  under  the 
form  of  stream,  brush,  or  glow,  and  so  parry  the 
violent  concentrated  explosion  commonly  attendant 
on  them.  This  result  ensues  whether  the  pointed 
conductor  be  affixed  to  the  charged  body  or  not — 
the  opposite  electrical  state  being  always  produced 
in  every  case  of  discharge.  Thus,  if  we  present  a 
pointed  metallic  body  to  the  conductor  of  the 
machine,  in  the  act  of  throwing  off  dense  and 
brilliant  sparks,  such  sparks  can  no  longer  be 
obtained  (p.  11) — the  electric  matter  being  silently 
drawn  off  by  the  point. 

Brush  discharge  exhibits  a  great  variety  of 
character  in  different  media,  its  color,  form,  and 
sound,  being  all  greatly  modified,  according  as  it 
takes  place  on  a  positive  or  negative  surface.  Ni¬ 
trogen  gas,  which  enters  in  the  proportion  of  four- 
fifths  into  the  composition  of  the  atmosphere,  has 
the  greatest  power  of  originating  this  kind  of 
discharge.  The  brushes  in  this  gas,  are  always 
fine  in  form,  light,  and  color ;  and  in  nitrogen 
rarefied  by  the  air-pump  the  effects  are  still  more 
striking. 

Brush  discharge  in  air  from  a  positive  point 
(p.  15)  is  frequently  diffuse  and  spreading,  pro¬ 
ducing  the  appearance  called  by  sailors  comazants, 
or  St.  Helmo’s  fires ;  from  a  negative  point  (p.  15) 
it  has  often  the  character  of  a  luminous  star,  exhibit¬ 
ing  the  appearances  mentioned  by  Pliny  and  other 
ancient  writers  (p:  21). 


48 


ARTIFICIAL  DISRUPTIVE  DISCHARGES. 


When  the  air  in  contact  with  a  metallic  con¬ 
ductor  is  rapidly  charging,  the  end  of  the  conductor 
will  often  become  covered  with  a  glow  of  lambent 
light,  producing  a  peculiarly  beautiful  appearance; 
this  is  greatly  increased  either  by  decreasing  the  at¬ 
mospheric  pressure,  or  by  augmenting  the  electrical 
force.  Faraday  produced  on  a  brass  ball  within  an 
exhausted  receiver,  a  glow  of  light  over  an  area  of 
two  inches.  The  glow  came  over  the  ball,  and 
gradually  increased  in  brightness  until  it  was  at  last 
very  luminous,  and  stood  up  like  a  low  flame  of 
half  an  inch  or  more  in  length,*  being  analogous 
to  one  of  the  natural  phenomena  already  mentioned 

(p.  21). 

When  the  discharge  is  assisted  by  traces  of  con¬ 
ducting  matter,  it  will  traverse  very  considerable 
distances.  Thus  a  trace  of  sulphuric  acid,  or  small 
particles  of  charcoal,  or  metallic  dust,  dispersed  over 
a  strip  of  glass,  will  enable  a  battery  to  produce  a 
brilliant  and  intensely  luminous  discharge,  over  a 
considerable  distance.  A  trace  of  smoke  will  in  like 
manner  facilitate  the  progress  of  the  explosion. 
When  the  intermediate  air  is  highly  rarefied  in  a 
tube  of  glass,  a  jar  may  be  discharged  through  it  to 
the  extent  of  several  feet,  sometimes  in  one  dense 
mass,  in  others  producing  bifurcations  and  various 
colored  streams. 

In  the  vacuum  of  a  well-boiled  barometer,  the 
electrical  light  is  frequently  of  a  beautiful  green 


*  Experimental  Researches,  p.  47. 


FURTHER  OBSERVATIONS  ON  THUNDER  CLOUDS.  49 


color,  and  in  media  of  different  kinds  varying  in 
density,  the  color  of  the  spark  is  altogether  changed. 
Thus  in  carbonic  acid  gas  it  is  white  and  vivid,  in 
hydrogen  gas  it  is  red  and  faint.  All  this  again  be¬ 
comes  modified  by  the  quantity  of  electricity,  and 
by  the  kind  and  form  of  the  conductors  from  which 
it  takes  place.  Considering,  therefore,  all  these 
circumstances,  it  is  not  at  all  surprising  that  we 
find  lightning  assuming  so  great  a  variety  of  ap¬ 
pearance. 

Further  Observations  on  Thunder  Ohuds. 

Although  the  disruptive  discharge  of  thunder¬ 
storms,  commonly  proceeds  at  once  through  the  air 
intermediate  between  the  charged  clouds  and  the 
earth,  yet  other  more  complicated  discharges  have 
been  supposed  to  occur,  in  consequence  of  electrical 
disturbances  between  distinct  and  distant  portions  of 
the  atmosphere,  in  which  the  surface  of  the  earth 
becomes  involved  as  a  line  of  discharge  between 
them.  The  Italian  philosopher,  Beccaria,  entertained 
opinions  of  this  kind ;  he  seemed  to  consider  it  im¬ 
possible  that  any  cloud  or  collection  of  clouds,  should 
contain  the  great  quantity  of  electricity  observed  in 
thunderstorms,  so  as  either  to  discharge  or  receive 
it.  He  states  that,  during  the  progress  of  a  storm, 
although  the  lightning  frequently  struck  the  earth, 
yet  the  clouds  were  the  next  moment  ready  to  make 
a  still  greater  discharge;  and  hence  he  concludes 
that  “the  electrical  matter  is  continually  darting 

from  the  clouds  in  one  place,  at  the  same  time  that 

3 


% 


50 


FURTHER  OBSERVATIONS 


it  is  discharged  from  the  earth  in  another.”  The 
knowledge,  however,  we  now  possess,  of  the  nature 
and  extent  of  electrical  action,  renders  it  quite  un¬ 
necessary  to  resort  to  such  hypothetical  views,  dn 
order  to  explain  this  phenomenon.  The  immense 
absorption  and  evolution  of  electricity  attendant  on 
chemical  and  other  changes  in  common  matter,  is 
quite  sufficient  to  account  for  the  apparently  great 
quantity  of  electricity  active  in  thunderstorms. 
Faraday  has  shown  by  strong  experimental  evi¬ 
dence,  that  the  quantity  of  electricity  holding  the 
elements  of  a  single  grain  of  water  in  chemical  com¬ 
bination,  is  equal  to  that  discharged  in  an  ordinary 
flash  of  lightning,  and  would,  if  discharged  under 
the  form  of  a  current  through  a  wire  of  platinum 
about  of  an  inch  in  diameter,  keep  it  red-hot 
in  the  air,  for  nearly  four  minutes.*  .The  simple 
view,  therefore,  which  we  have  taken  of  the  electri¬ 
cal  conditions  of  a  thunderstorm,  is  in  no  way  em¬ 
barrassed  by  any  difficulty  arising  out  of  the  great 
quantity  of  electricity  liable  to  be  discharged.  Be¬ 
sides,  it  is  not  clear  that  the  quantity  is  so  great  in 
relation  to  conducting  bodies,  as  might  at  first  be 
supposed.  It  is  to  be  recollected,  that  we  often 
judge  of  the  quantity  of  electricity  present,  by  very 
deceptive  effects, — as  by  the  light  of  the  spark,  the 
noise  and  expansive  force  of  the  discharge,  and  by 
the  damage  done  to  imperfect  conducting  matter. 
Now,  we  have  seen  (p.  31)  that  comparatively  small 


*  Experimental  Researches  in  Electricity,  p.  250. 


ON  THUNDERSTORMS. 


51 


quantities  of  electricity  will  produce  intense  effects 
of  this  kind ;  and  it  is  doubtful  whether  any  quan¬ 
tity  of  electricity  ever  discharged  in  a  single  flash 
of  lightning  has  been  sufficient  to  melt  a  copper 
rod  a  foot  in  length  and  three-fourths  of  an  inch  in 
diameter. 

The  general  condition  of  a  thunderstorm  is,  as 
already  observed,  (p.  5),  the  charging  and  discharg¬ 
ing  of  a  stratum  of  air  intermediate  between  the 
masses  of  cloud  and  the  earth,  or  otherwise  interme¬ 
diate  between  two  masses  of  clouds  in  opposite 
electric  states;  the  source  of  the  charge  being  the 
evolution  of  electricity  in  consequence  of  certain 
physical  changes  in  the  state  and  condition  of  the 
atmosphere.  Discharges  of  lightning  produced  by 
this  state  of  things,  may  arise  during  the  formation 
or  presence  of  clouds  in  a  given  place,  or  during 
their  formation  and  motion  through  the  air,  by 
which  a  large  stratum  of  polarized  particles  is  swept 
along  over  the  earth’s  surface  ;  or  they  may  arise 
from  the  motion  of  an  upper  current  of  cloud  over 
a  large  track  of  atmosphere,  which  has  from  any 
previous  train  of  circumstances,  become  polarized ; 
or  otherwise,  from  the  operation  of  successive  super¬ 
imposed  strata  of  air  and  clouds,  reaching  to  the 
surface  of  the  earth ;  or  otherwise,  from  the  opera¬ 
tion  of  distant  and  distinct  portions  of  the  atmo¬ 
sphere,  oppositely  charged,  and  which  may  hence 
discharge  into  each  other,  under  a  great  variety  of 
conditions. 


52 


KEECTRICAL  DISCHARGES. 


Electrical  Discharges, 

Thunderstorms  arising  out  of  a  rapid  formation 
of  vapor,  and  in  a  limited  portion  of  the  air,  as 
illustrated  in  fig.  1,  (p.  13,)  have  been  well  described 
by  Beccaria.  “  The  first  appearance  of  a  thunder¬ 
storm,”  he  says,  “  generally  happens  when  there  is 
little  or  no  wind  ;  there  is  one  dense  cloud  or  more, 
increasing  very  fast  in  size,  and  rising  into  the 
higher  regions  of  the  air.  The  lower  surface  is 
black,  and  nearly  level,  but  the  upper  is  finely 
arched,  and  well-defined.  Many  of  these  clouds 
seem  piled  one  over  another,  all  arched  in  the  same 
way,  but  they  keep  continually  uniting,  swelling, 
and  extending  their  arches.  At  the  time  of  the 
rising  of  this  cloud,  the  atmosphere  is  generally  full 
of  a  great  number  of  separate  clouds  of  whimsical 
and  irregular  shapes,  and  apparently  motionless. 
All  these  upon  the  appearance  of  the  thunder  cloud 
draw  towards  it,  become  more  uniform  in  their 
shape,  and  at  length  form  with  it  one  common  mass. 
Sometimes  the  thunder  cloud  will  swell  very  fast 
without  the  conjunction  of  such  clouds,  and  when 
it  is  grown  to  a  great  size,  its  lower  surface  is  fre¬ 
quently  ragged,  and  swells^ into  large  protuberances 
which  bend  uniformly  toward  the  earth ;  some¬ 
times  one  whole  side  of  the  cloud  has  an  inclination 
toward  the  earth.  When  the  eye  is  under  the 
thunder  cloud,  it  is  at  last  seen  to  darken  fearfully, 
and  a  number  of  small  clouds,  the  origin  of  which  is 
never  detected,  drive  about  it  in  uncertain  direc- 


ELECTRICAL  DISCHARGES. 


53 


tions.  Rain  and  hail  about  this  time  fall  in  abun¬ 
dance.  During  the  swelling  and  extension  of  the 
cloud  over  a  large  tract  of  country,  lightning  darts 
through  its  mass,  and  at  length  strikes  toward  the 
earth  in  opposite  places ;  the  longer  the  lightning 
continues,  the  rarer  the  cloud  becomes,  till  at  length 
it  breaks  up  in  different  places,  and  shows  a  clear 
sky.”* 

Captain  Ward,  R.  N".,  gives  the  following  inter¬ 
esting  account  of  the  phenomena  observed  by  him 
during  a  thunderstorm  in  the  Bay  of  Honduras  in 
the  West  Indies,  whilst  he  was  in  command  of  his 
Majesty’s  ship  Pelimn^  in  the  autumn  of  the  year 
1806.  “  The  night  was  nearly  calm,  and  the  heat 

oppressive;  heavy  black  clouds  intensely  charged 
with  the  electric  fluid,  overspread  the  earth,  and 
about  midnight,  after  a  little  whirl  of  wind,  began 
to  approach  it.  A  discharge  of  lightning  of  the 
most  splendid,  and  at  the  same  time  most  awful 
character,  speedily  ensued.  The  electric  fluid  seemed 
to  pour  down  upon  the  earth  and  sea  in  repeated 
streams,  occasionally  illuminating  every  thing  about 
us  with  a  brilliancy  surpassing  noon-day,  but  leaving 
us  at  the  next  instant  in  pitchy  darkness.  This 
fearful  display,  attended  by  roaring  peals  of  thunder, 
lasted  about  an  hour,  during  which  one  of  the  dis¬ 
charges  fell  on  our  main-royal  mast-head,  shivered 
it,  together  with  the  top-gallant  mast  and  topmast 
in  atoms,  scattering  the  fragments  to  an  immense 


*  Lettere  delV  Elettrumo,\).  151  to  167. 


64 


ELECTRICAL  DISCHARGES. 


distance,  so  that  not  a  piece  of  any  size  could  be 
found.  The  discharge  continued  its  course  with 
damage  along  the  mainmast  in  an  irregular  spiral 
form  down  to  the  very  heel  and  step  of  the  mast, 
where  it  disappeared.” 

One  of  the  most  awful  accounts,  however,  of  a 
thunderstorm  at  sea  is  that  given  by  an  intelligent 
observer,  present  as  a  passenger  in  the  splendid 
American  packet-ship  New-  York^  which  was  struck 
and  damaged  by  lightning  in  the  Gulf-stream, 
April  19th,  1827,  in  her  passage  from  New-York  to 
Liverpool.  “  About  half-past  five  in  the  morning, 
being  in  our  berths,  we  were  roused  by  a  sound  like 
the  report  of  heavy  cannon  close  to  our  ears.  In  a 
moment  we  were  all  out.  From  the  deck  the 
word  was  quickly  passed  that  the  ship  had  been 
struck  by  lightning,  and  was  on  fire.  Every  one 
ran  on  deck ;  there,  all  the  elements  were  in  violent 
commotion :  it  had  been  broad  day,  but  so  dark,  so 
dense,  and  so  close  upon  us  were  the  clouds,  that 
they  produced  almost  the  obscurity  of  night.  There 
was  just  sufficient  light  to  give  a  bold  relief  to  every 
object  in  the  appalling  scene ;  the  rain  poured  down 
in  torrents,  mingled  with  hailstones  as  large  as  fil¬ 
berts  ;  these  lay  upon  the  deck  nearly  an  inch 
thick ;  overhead  blazed  the  lightning  on  all  sides, 
accompanied  by  simultaneous  reports ;  the  sea  ran 
mountains  high,  and  the  ship  was  tossed  rapidly 
from  one  sea  to  another.  One  appearance  was  pe¬ 
culiarly  remarkable :  the  temperature  of  the  water 
was  74°  of  Fahrenheit,  whilst  that  of  the  atmosphere 


ELECTRICAL  DISCHARGES 


55 


was  only  48°.  This  caused,  by  evaporation  and  con¬ 
densation,  immense  clouds  of  vapor,  which  ascend¬ 
ing  in  columns  all  around  us,  exhibited  the  appear¬ 
ance  of  innumerable  pillars  supporting  a  massive 
canopy  of  clouds.  In  all  directions  might  be  seen 
water-spouts,  which  rising  fearfully  to  the  clouds, 
seemed  actually  to  present  to  the  eye  a  combination 
of  all  the  elements  for  the  destruction  of  every  thing 
on  the  face  of  the  deep.”  These  accounts  afford 
highly  instructive  examples  of  the  spontaneous  evo¬ 
lution  of  electricity  in  the  atmosphere,  giving  rise  to 
a  vast  electrical  disturbance,  and  subsequent  disrup¬ 
tive  discharges  (p.  15). 

The  altitude  of  the  masses  of  cloud,  forming  the 
upper  terminating  plane  of  the  electrified  system, 
does  not  appear  to  be  so  considerable  as  their  hori¬ 
zontal  dimensions,  which  not  unfrequently  extend 
over  a  large  tract  of  country,  producing  almost 
simultaneous  discharges  in  various  places.  Admiral 
Eoss  states,  that  the  storm  which  shivered  the  masts 
of  the  Desiree  in  Port  Antonio,  Jamaica,  in  the 
autumn  of  1803,  was  witnessed  by  an  observer  some 
short  distance  up  the  adjacent  hill.  It  appeared  to 
take  place  close  under  him,  during  a  fine  clear,  star¬ 
light  evening  overhead. 

On  the  night  of  the  14th  of  April,  1718,  a  thun¬ 
derstorm  occupied  the  coast  of  Brittany  between 
Landerneau  and  St.  Pol  de  Leon,  and  ’damaged  no 
less  than  twenty-four  church  towers.*  In  1774  a 


3* 


*  Annuaire  pour  1838,  p.  479. 


56 


ELECTRICAL  DISCHARGES. 


severe  thunderstorm  spread  itself  over  London.  The 
lightning  damaged  St.  Peter’s  church  considerably, 
and  at  the  same  time  several  other  discharges  occur¬ 
red  in  various  places  far  distant  from  each  other.  A 
Dutch  ship  in  the  river  off  the  Tower  was  struck,  also 
the  obelisk  in  St.  Greorge’s  fields,  Southwark,  together 
with  a  chimney  at  Lambeth,  and  a  house  at  Yauxhall.* * * § 
On  the  11th  January,  1815,  another  thunderstorm 
occupied  no  less  a  space  than  that  contained  between 
the  North  Sea  and  the  Rhenish  provinces,  and  severe¬ 
ly  damaged  twelve  church  towers  in  various  parts  of 
this  extensive  tract,  f 

The  electrical  disturbance  is  sometimes  so  very 
rapidly  progressive,  that  repeated  discharges  are  ob¬ 
served  to  occur  in  the  same  place,  in  quick  succession. 
The  church  and  buildings  of  the  abbey  of  Notre 
Dame,  in  the  town  of  Ham,  in  France,  was,  during 
the  night  of  the  25th  April,  1760,  struck  three  times 
in  the  short  interval  of  twenty  minutes,  and  the 
whole  burnt  to  the  ground.^  His  Majesty’s  ship 
Hyacinth  had  first  her  fore-topmast,  then  her  main- 
topmast  rent  in  pieces  by  two  discharges  which 
followed  close  upon  each  other.  § 

His  Majesty’s  ship  Madagascar ^  in  coming  to  an 
anchor  in  the  Corfu  Channel,  in  January,  1829,  was 
struck  by  lightning  no  less  than  five  times  within 
two  hours ;  the  sails  were  set  on  fire,  and  other 

*  Phil.  Trans.y  vol.  Ixiv.  for  1774. 

f  Annuaire  pour  1838,  p.  481. 

t  Idem,  p.  482. 

§  Report  of  Commission,  p.  75. 


ELECTRICAL  DISCHARGES. 


57 


damage  done.  His  Majesty’s  ship  JEtna  was  in  the 
same  storm,  and  not  far  distant ;  she  experienced  re- 
-  peated  discharges  :  “the  descent  of  the  electric  fluid 
was  frequent  and  at  very  short  intervals.”  * 

His  Majesty’s  frigate  Olorinde  was  struck  and 
damaged  by  lightning,  on  the  coast  of  Ceylon,  in  the 
spring  of  the  year  1813.  The  following  is  a  very 
clear  and  circumstantial  account  of  the  phenomena, 
by  Captain  Briggs,  E.  N.,  who  commanded  the  ship. 

The  weather  was  moderate.  About  three  in  the 
afternoon  we  observed  a  dark  cloud  approaching  the 
ship  from  the  windward  quarter :  this  induced  me  to 
clew  up  the  topsails.  About  an  hour  afterwards,  the 
ship  was  struck  by  lightning :  the  cloud  we  had  ob¬ 
served,  was  charged  with  electricity,  and  had  burst 
on  the  ship.  The  mainmast  was  shivered  in  pieces ; 
only  a  wreck  remained.  Three  men  were  killed, 
and  many  hurt.” 

How  it  is  clear,  that  in  this  instance,  the  dis¬ 
ruptive  discharge  was  caused  by  the  progressive 
motion  of  a  charged  cloud,  driven  by  an  upper 
current,  upon  a  comparatively  tranquil  air,  but  pos¬ 
sibly  in  a  polarized  state,  sweeping  along  with  it  a 
portion  of  charged  atmosphere,  and  accumulating 
forces,  sufiicient  to  make  it  approach  the  earth, 
within  a  distance  at  which  the  forces  could  neutralize 
through  the  intermediate  stratum. 

The  following  is  a  similar  instance,  related  by 
Captain  Haydon,  E.  H.,  in  which  the  whole  atmo¬ 
sphere  and  cloud  travelled  together  in  the  direction 

*  Report  of  Commission,  p.  87. 

3^ 


58 


ELECTRICAL  DISCHARGES. 


of  the  wind.  “His  Majesty’s  ship  Cambrian^  off  Ply¬ 
mouth,  February  22,  1799,  strong  gales  and  squally; 
observed  a  tremendous  squall  coming  down  upon  us ; 
turned  the  hands  up  to  clew  up  the  close-reefed  top¬ 
sails.  Whilst  they  were  so  employed,  a  ball  of  fire 
struck  the  topmast-head,  killed  two  men  and  wounded 
many  others.  The  number  taken  below  amounted 
to  about  twenty.” 

The  case  of  His  Majesty’s  ship  Topaze^  struck  by 
lightning  in  the  West  Indies,  in  July,  1802,  is  another 
remarkable  instance  of  this  source  of  disruptive  dis¬ 
charge.  Captain  H.  Edwards,  K.  H.,  who  was  in  the 
ship  at  the  time,  says,  “When  off  the  west  end  of 
St.  Domingo,  about  two  or  three  leagues  from  the 
shore,  we  were  becalmed.  About  midnight  a  light 
breeze  came  off  the  land,  bearing  a  dark  isolated 
cloud;  the  cloud  began  to  discharge  its  lightning 
within  an  apparently  short  distance  of  the  ship,  and 
after  five  or  six  vividly  forked  flashes,  struck  our 
mizzen  royal-mast,  and  passed  down  the  mizzen¬ 
mast,  shivering  and  rending  the  spars  in  its  course.” 

It  appears  that  the  light  breeze  from  the  shore 
enabled  them  to  get  the  ship’s  head  the  right  way, 
so  as  to  lay  her  with  her  stern  to  the  shore :  hence 
the  mizzen-mast  was  the  mast  first  acted  on  by  the 
cloud. 

A  great  variety  of  instances  might  be  quoted,  in 
confirmation  of  disruptive  discharges  being  produced 
on  the  principles  already  explained  (p.  12) :  they  all 
differ  from  the  state  of  things  observable  in  more 
stationary  thunderstorms  (p.  52)  in  this,  that  whilst 


ASCENDING  STROKE. 


59 


in  such  thunderstorms,  there  is  often  a  rapid,  and 
continuous  series  of  discharges  produced  by  the 
spontaneous  evolution  of  electricity  in  one  place : 
we  trace  in  the  progress  of  highly  electrified  clouds, 
deliberate  discharges  of  a  passing  kind,  few  in  num¬ 
ber,  in  some  instances  not  extending  beyond  one  or 
two  at  the  furthest. 

Electrical  disturbances,  involving  similar  condi¬ 
tions,  but  of  a  more  complicated  character,  sometimes 
proceed  with  continued  destructive  effects  over  a 
long  tract  of  country,  the  atmosphere  appearing  to 
assume,  during  the  progress  of  the  masses  of  electri¬ 
fied  cloud,  an  intensely  charged  state.  Such  storms 
have  been  observed  to  pass  from  the  southern  shores 
of  England  to  the  north  of  Scotland  and  Ireland. 
A  thunderstorm  of  this  kind  occurred  in  July,  1827. 
It  began  on  the  south-west  coast  of  Devonshire  on 
Sunday  evening,  reached  Cheltenham  the  same  night, 
and  Glasgow  the  next  morning,  the  atmosphere 
throughout  this  extent  appearing  to  undergo  a  rapid 
and  progressive  change.* 

.  Ascending  Stroke. 

Sometimes  the  thunderbolt  passes  from  the  earth 
to  the  clouds,  and  in  this  case  it  is  called  by  some 
philosophers  the  “ascending  stroke,”  by  others  “the 
returning  stroke.”  Facts  are  not  wanting  to  indicate 
the  progress  of  electricity  upward.  The  Marquis 
Maffei  was  the  first  who  observed  this  curious  phe- 


*  Provincial  and  London  Journals. 


60 


ASCENDING  STROKE. 


nomenon.  He  distinctly  saw,  during  a  storm,  the 
lightning  issue  from  the  ground  with  a  loud  noise. 
The  Abbe  Lioni  and  M.  Segnier  of  Nismes,  saw  the 
lightning  rise  in  the  form  of  flame  six  feet  high, 
followed  by  a  loud  noise. 

One  of  the  most  interesting  cases  of  the  ascend¬ 
ing  stroke  has  been  recorded  by  John  Williams,  Esq. 
It  took  place  upon  the  hills  above  the  village  of  Great 
Malvern,  on  the  1st  July,  1826.  A  party  had  taken 
refuge  from  the  storm  in  a  circular  building  roofed 
with  sheet  iron,  and  one  of  the  ladies  on  entering 
the  hut  expressed  her  alarm  lest  the  lightning  should 
be  attracted  by  the  iron  roof.  They  had  scarcely 
entered  their  retreat,  and  were  about  to  partake  of 
some  refreshment,  when  a  violent  storm  of  thunder 
and  lightning  came  on  from  the  west.  About  forty- 
five  minutes  past  two,  a  gentleman  who  stood  at  the 
eastern  entrance,  saw  a  ball  of  fire  which  seemed  to 
him  moving  on  the  surface  of  the  ground.  It  in¬ 
stantly  entered  the  hut,  forcing  him  several  paces 
forward  from  the  doorway.  On  his  recovering  from 
the  shock,  he  found  his  sisters  on  the  floor  of  the  hut, 
fainting,  as  he  imagined,  from  terror.  Two  of  the 
ladies  had  died  instantly ;  another  lady,  and  the  rest 
of  the  party,  were  much  injured.  The  explosion 
which  followed  the  flash  of  lightning,  was  said,  by 
the  inhabitants  of  the  village,  to  have  been  terrific. 
Mr.  Williams,  who  immediately  examined  the  hut, 
found  a  large  crack  in  the  west  side  of  the  building, 
which  passed  upward  from  near  the  ground  to  the 
frame  of  a  small  window,  above  which  the  iron  roof 


ASCENDING  STROKE. 


61 


was  a  little  indented.  Mr.  Williams  conceived  it  to 
be  quite  clear,  from  the  place  of  the  fragments  of 
stone  and  other  appearances,  that  the  clouds  were 
negatively  electrified  during  this  storm.* 

A  very  curious  instance  of  the  ascending  stroke 
is  related  by  Gr.  F.  Kichter,  in  his  work  on  thunder. 
He  informs  us  that  in  the  cellar  belonging  to  the 
Benedictine  monks  of  Fontigno,  while  the  servants 
were  employed  in  pouring  into  a  cask  some  wine 
which  had  been  just  boiled,  a  fine  light  flame  ap¬ 
peared  round  the  funnel,  and  they  had  scarcely  finished 
their  operations,  when  a  noise  like  thunder  was  heard ; 
the  cellar  was  instantly  filled  with  fire  ;  the  cask  was 
burst  open,  although  hooped  with  iron,  the  staves 
were  thrown  with  prodigious  violence  against  the 
wall,  and,  on  examination,  a  hole  of  three  inches  di¬ 
ameter  was  found  in  the  bottom  of  the  cask.f 

On  the  24th  of  February,  1774,  lightning  struck 
the  steeple  of  the  village  of  Kouvroi,  to  the  north¬ 
west  of  Arras.  A  pavement  composed  of  large  blue 
stones,  which  was  laid  under  the  steeple  was  violently 
raised  upw'ard. 

In  the  summer  of  1787  lightning  struck  two  per¬ 
sons  who  had  taken  refuge  under  a  tree  near  the 
village  of  Tacon,  in  Beaujalois.  Their  hair  was 
driven  upward  and  found  upon  the  top  of  the  tree.  A 
ring  of  iron  which  was  upon  the  shoe  of  one  of  these 
persons  was  found  afterwards  suspended  on  one  of  the 
upper  branches. 

*  Encyclopcedia  Britannia,  vol.  8,  p.  619. 
f  London  Evcyclopcedica,  vol.  8,  p.  59. 


62 


ASCENDING  STROKE. 


On  the  29th  of  August,  1808,  lightning  struck  a 
small  building  near  the  hospital  of  Salpetri^re  in 
Paris.  A  laborer  who  was  in  it  was  killed,  and  after 
the  event  the  pieces  of  his  hat  were  found  incrusted 
on  the  ceiling  of  the  room. 

When  trees  have  been  barked  by  lightning,  it 
frequently  happens  that  the  bark  is  stripped  from  the 
base  upward  to  a  certain  height,  and  the  upper  part 
of  the  tree  is  untouched.  This  occurred  with  several 
trees  in  the  Champs  Elysees,  at  Paris,  in  a  storm  which 
took  place  in  June,  1778. 

The  leaves  of  trees  which  have  been  struck  by 
lightning  often  exhibit  the  effects  of  heat  on  their 
lower  surfaces,  but  not  at  all  on  their  superior  sur¬ 
faces. 

Among  the  numerous  manifestations  of  the  dis¬ 
charge  of  electric  matter  from  the  surface  of  the  earth, 
one  of  the  most  circumstantial  and  authentic  is  due 
to  Brydone,  who,  being  on  the  spot  where  the  oc¬ 
currences  took  place,  was  in  part  witness  to  them,  and 
collected  the  particulars  from  other  eye-witnesses 
with  scrupulous  care. 

On  the  10th  July  1785,  a  storm  broke  out  be¬ 
tween  noon  and  one  o’clock,  in  the  neighborhood  of 
Coldstream.  During  its  continuance,  there  occurred 
in  the  surrounding  country  several  remarkable  acci¬ 
dents. 

A  woman  who  was  cutting  grass  on  the  banks  of 
the  Tweedy  was  suddenly  thrown  down  without  any 
apparent  cause.  She  called  her  companions  immedi¬ 
ately  to  her  aid,  and  told  them  that  she  received  a 


ASCENDING  STROKE. 


63 


sudden  and  violent  blow  on  the  soles  of  her  feet,  but 
whence  it  proceeded  she  could  not  tell.  At  the  mo¬ 
ment  this  happened  there  was  neither  thunder  nor 
lightning. 

A  shepherd  attached  to  a  farm  called  Lennel 
Hill,  saw  a  sheep  suddenly  fall,  which  the  moment 
before  appeared  in  perfect  health.  He  ran  to  raise 
it  from  the  ground,  and  found  it  stiff  dead.  The 
storm  was  then  approaching,  but  distant. 

Two  coal-wagons,  driven  by  two  boys,  seated  on 
the  benches  in  front  of  them,  had  just  crossed  the 
Tweedy  and  were  in  the  act  of  ascending  a  hill  on  the 
banks  of  the  river,  when  a  loud  explosion  was  heard 
like  the  report  of  several  guns  fired  nearly  together, 
and  unattended  by  any  rolling  or  continued  sound 
like  that  which  usually  accompanies  thunder.  At 
the  moment  of  this  explosion  the  boy  who  drove  the 
second  wagon  saw  the  foremost  wagon  with  the  two 
horses  and  driver  suddenly  fall  to  the  ground,  the 
coal  being  scattered  about  in  all  directions.  On  ex¬ 
amination,  the  driver  and  horses  were  found  to  be 
stiff  dead.  The  coal  which  was  dispersed,  had  the 
appearance  of  having  been  for  some  time  in  the  fire. 
At  the  points  where  the  tires  of  the  wheels  rested  at 
the  time  of  the  explosion,  the  ground  was  found  to 
be  pierced  by  two  circular  holes,  which  being  exam¬ 
ined  by  Brydone  half  an  hour  after  the  occurrence, 
emitted  a  strong  odor  resembling  that  of  ether.  The 
tires  of  the  wheels  showed  evident  marks  of  fusion 
at  the  points  which  were  in  contact  with  the  road  at 
the  moment  of  the  explosion,  and  at  no  other  part. 


64 


ASCENDING  STROKE. 


The  hair  was  singed  on  the  legs  and  under  the  bel¬ 
lies  of  the  horses,  and  by  a  careful  examination  of 
the  marks  left  in  the  dust  of  the  road  where  they 
fell,  it  was  apparent  that  they  must  have  been  struck 
suddenly  stone  dead,  so  that  no  life  remained  when 
they  touched  the  ground.  Had  there  been  any  con¬ 
vulsive  struggle,  the  marks  would  have  been  visible. 
The  body  of  the  driver  was  scorched  in  different  pla¬ 
ces,  and  his  dress,  shirt,  and  particularly  his  hat, 
were  reduced  to  rags.  A  strong  odor  proceeded 
from  them. 

All  the  witnesses  of  this  occurrence  agreed,  that 
no  luminous  appearance  whatever  attended  it.  The 
driver  of  the  second  wagon  was  conversing  with  his 
comrade,  and  was  looking  toward  him  at  the  mo¬ 
ment  he  was  struck  down,  being  at  about  twenty 
yards  behind  him,  but  saw  no  light.  A  shepherd 
standing  in  an  adjacent  field,  told  Mr.  Brydone  that 
he  had  his  eye  on  the  wagon  at  the  very  instant  of 
the  explosion,  but  he  saw  no  light.  He  saw  a  vortex 
of  dust  arise  at  the  place  of  the  explosion,  but  unac¬ 
companied  by  any  luminous  appearance.  Finally, 
Mr.  Brydone  himself  at  the  moment  of  the  event  was 
standing  at  an  open  window,  with  a  watch  in  his , 
hand,  explaining  to  the  persons  around  him  the 
method  of  calculating  the  distance  of  the  lightning 
by  observing  the  interval  between  the  flash  and  the 
thunder,  and  he  heard  the  explosion,  but  perceived 
no  light.* 

Professor  Dewey,  D.  D.,  of  Eochester  University, 

*  Dr.  Lardner's  Lectures  on  Science  and  Art,  Vol.  II,  p.  72. 


ASCENDING  STROKE. 


65 


related  to  the  writer  some  few  months  since,  that 
during  his  connection  with  Williamstown  College, 
Mass.,  a  church  in  South  Williamstown  was  struck 
by  lightning.  The  house  was  carefully  examined 

himself  after  it  was  struck,  when  he  saw  leaves 
of  flowers  that  had  grown  by  the  walls  of  the 
church,  lodged  in  the  cobwebs  up  under  the  eaves. 

Some  time  last  summer  Mr.  Platt’s  house.  Deep 
River,  Connecticut,  was  struck  by  lightning.  After 
the  accident,  the  house  was  carefully  examined  by 
myself  and  many  others.  It  was  evidently  an  in¬ 
stance  of  the  “  ascending  stroke.”  The  front  part  of 
the  house,  including  the  entire  length  of  the  wing 
attached,  was  traversed  by  the  lightning,  leaving 
marks  of  terrific  violence  wholly  unaccountable,  un¬ 
less  done  by  an  upward  force. 

W e  have  multiplied  the  number  of  instances  un¬ 
der  this  head,  for  two  reasons :  First,  because  so 
many  of  those  little  read  in  electrical  science  utterly 
disbelieve  the  existence  of  an  upward  stroke,  and 
even  laugh  at  the  idea  as  absurd  and  whimsical. 
Secondly,  because  an  intelligent  belief  in  an  upward 
stroke  has  an  important  relation  to  the  application 
of  lightning  conductors  for  the  protection  of  build¬ 
ings,  as  we  shall  presently  see. 

Various  electrical  phenomena,  of  a  very  interest¬ 
ing  kind,  have  been  observed  by  travellers,  when 
ascending  lofty  mountains.  In  1767,  M.  M.  Saus- 
sure,  Pictet,  and  J allabert,  when  on  the  top  of  Mount 
Breven,  received  small  electric  shocks  at  their  finger- 
ends,  by  stretching  out  their  arms,  and  a  whistling 


66 


ASCENDING  STROKE. 


nojse  even  accompanied  them.  The  gold  button  on 
M.  Saussure’s  hat  yielded  distinct  sparks.  In  1814, 
a  party  of  Englishmen  experienced  similar  effects  on 
Mount  ^tna,  during  a  storm  of  thunder  and  light¬ 
ning,  accompanied  by  a  fall  of  snow.  One  of  the 
party  felt  his  hair  moving,  and  upon  raising  his 
hand  to  his  head,  a  buzzing  sound  issued  from  his 
fingers.  The  rest  of  the  party  experienced  the  same 
sensations,  and  by  moving  their  hands  and  fingers 
they  produced  a  variety  of  musical  sounds,  audible 
at  the  distance  of  forty  feet.  On  the  27th  of  June, 
1825,  Dr.  Hooker  and  a  party  of  botanists  witnessed 
effects  like  those  described,  during  a  fall  of  snow  on 
Ben-Hevis,  when  there  was  no  thunderstorm.  The 
snow  fell  very  heavily  for  nearly  two  hours.  Soon 
after  it  began,  a  hissing  sound  was  heard  every 
where  around  them,  and  continued  about  an  hour 
and  a  half.  It  seemed  to  proceed  from  every  point 
in  the  vicinity;  and  on  arriving  at  the  cairn  on  the 
summit  of  the  mountain,  they  could  almost  determine 
the  stones  from  which  the  electricity  issued.  The 
hair  of  several  of  the  party  exhibited,  when  touched, 
the  usual  electrical  phenomena.* 


*  Encyclopcedia  Britannica,  vol.  viii.  p.  620. 


SECTION  II. 


APPLICATION  OF  METALLIC  CONDUCTORS  TO 
THE  DEFENCE  OF  BUILDINGS  AND  SHIP¬ 
PING  FROM  LIGHTNING. 


Laws  of  Disruptive  Discharges — Observed  effects  on  Buildings  and 
Shipping — Practical  results  of  the  preceding  Inquiries — Jla- 
ture  and  operation  of  Lightning  Rods — Laws  of  Electrical  Con¬ 
duction — Mechanical  effects  of  the  Disruptive  Discharge — What 
quantity  of  Metal  is  requisite  in  the  construction  of  a  Lightning 
Rod — How  far  does  its  protecting  power  extend. 


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SECTION  11. 


Laws  and  Operation  of  Disruptive  Discharge. 

Whatever  may  be  the  theoretical  views  entertained 
relative  to  the  immediate  source  of  lightning,  and  the 
manner  in  which  disruptive  electrical  discharges  oc¬ 
cur  in  nature,  it  will  be  well  to  bear  in  mind,  that  all 
such  discharges,  have  nevertheless  one  common  char¬ 
acter, — all  produce  similar  effects, — and  are  all  gov¬ 
erned  by  the  same  laws.  We  propose,  therefore,  to 
consider  these  laws  more  particularly,  with  a  view 
of  arriving  at  certain  practical  deductions,  immedi¬ 
ately  bearing  on  the  question  of  the  defence  of  build¬ 
ings  and  shipping  from  lightning. 

If  we  attentively  examine  the  many  recorded  in¬ 
stances  in  which  buildings  and  ships  have  been  dam¬ 
aged  by  lightning,  the  course  of  the  discharge  may 
generally  be  traced ;  and  this  course  is  invariably 
determined  through  a  given  line  or  lines  which,  upon 
the  whole,  oppose  the  least  resistance  to  the  neutrali¬ 
zation  of  the  electrical  forces.  Both  space  and  time 
are,  as  it  were,  economized  in  the  restoration  of  the 


70 


LAWS  AND  OPERATION  OF 


electrical  equilibrium  (pp.  4,  5);  for  however  small  we 
assume  the  duration  of  the  discharge  to  be,  or  how¬ 
ever  limited  the  distance  through  which  it  strikes, 
both  these  quantities  would  become  still  less,  were 
other  lines  of  transit  provided  of  still  less  resistance. 
This  is  the  leading  phenomenon  of  all  disruptive  dis¬ 
charges  ;  hence  lightning  seizes  upon  such  bodies  as 
lie  convenient  and  ready  for  its  purpose,  absolutely 
avoiding  other  bodies,  however  near,  from  which  it 
can  receive  no  assistance.  And  it  may  be  further 
observed,  as  a  most  wonderful  and  interesting  fact, 
that  at  the  instant  before  the  explosion  takes  place, 
the  stream  of  electricity,  in  the  act  of  moving  to  re¬ 
store  the  equilibrium  of  distribution,  feels  its  way  as 
it  were  in  advance,  and  absolutely  marks  out  the 
course  it  is  about  to  take,  an  inductive  action  being 
impressed  upon  such  bodies  as  happen  to  lie  in  the 
line  or  lines  of  least  resistance ;  this  previous  induc¬ 
tion,  by  a  sort  of  foresight,  determines  the  course  of 
the  discharge.  Its  progress  therefore  is  not,  as  many 
imagine,  left  to  the  chances  of  the  instant,  to  be,  as 
it  were,  attracted  or  drawn  aside  by  metallic  bodies 
at  any  given  point ;  on  the  contrary,  the  whole  course 
of  a  stroke  of  lightning  is  already  fixed  and  settled, 
before  the  discharge  takes  place. 

The  evidence  deducible  from  observation  as  well 
as  from  physical  investigation,  is  most  conclusive  on 
this  point.  It  is  quite  clear,  from  what  has  been 
already  shown  (p.  15),  that  any  artificial  elevation 
on  the  earth’s  surface  is,  in  respect  of  a  thunderstorm, 
a  mere  point  in  one  of  the  terminating  planes  of  a 


DISRUPTIVE  DISCHARGE.  Il 

great  electrical  disturbance.  The  electrical  forces 
cannot  therefore  be  supposed  to  operate  exclusively 
between  such  an  elevation  and  a  charged  cloud.  A 
building  or  ship,  is  struck  by  lightning  only  in  con¬ 
sequence  of  its  being  a  point  in  one  of  the  electrified 
surfaces ;  in  short,  a  heterogeneous  mass,  acciden¬ 
tally  placed  in  a  position  to  facilitate  the  neutraliza¬ 
tion  of  the  electrical  forces  in  a  given  direction,  ex¬ 
tending,  perhaps,  over  many  square  miles  of  cloud 
and  opposed  sea  or  land  (p.  55). 


Fig.  10. 


By  way  of  illustration,  let  P  N  (fig.  10)  represent 
the  opposed  terminating  surfaces  of  the  clouds  and 
sea  at  the  time  of  a  thunderstorm,  and  n  the  position 
of  a  ship  at  the  instant  of  discharge ;  let  a  5  be  the 
point,  in  which  from  any  determining  cause,  the  par¬ 
ticles  of  the  intervening  air  give  way.  Imagine  fur¬ 
ther,  that  there  were  presented  for  the  course  of  the 


12 


LAWS  AND  OPERATION  OF 


discharge,  such  lines  of  transit,  sls  abcd^  ah  ah  /k, 
n  5  g  N  ;  then  the  question,  whether  the  ship  N  would 
be  struck  by  lightning,  would  depend  on  the  respec¬ 
tive  resistances,  in  the  direction  of  these  lines ;  it 
might  so  happen,  that  the  resistance  in  the  direction 
ah  c  d,  although  very  near  the  vessel,  might,  from  a 
variety  of  causes,  be  so  much  less  than  in  any  one  of 
the  other  lines,  that  the  discharge  would  not  touch 
the  ship  at  all.  Conversely,  the  resistance  might 
be  greatei'  in  the  direction  ah  c  d  than  in  any  other, 
in  which  case  the  discharge  would  become  deter¬ 
mined  through  the  ship,  and  one,  two,  or  three,  of 
the  masts,  would  be  struck  by  a  division  of  the  spark, 
in  the  way  already  stated  (pp.  35,  86),  according  to  the 
equality  or  difference  of  the  resistance  in  these  di¬ 
rections. 

We  must  not,  however,  proceed  too  hastily  with¬ 
out  verifying  principles  by  an  appeal  to  experience  : 
for  however  perfect  theoretical  views  of  such  ques¬ 
tions  may  be,  it  is  still  always  desirable  to  adhere 
carefully  to  facts. 

Her  Majesty’s  cutter  Haioh^  was  struck  by  light-  - 
ning  in  Broadhaven  Eoads  on  the  21st  of  January, 
1840,  and  seriously  damaged.  About  the  same  time, 
the  electrical  discharge  fell  so  near  the  Neptune^  a 
small  revenue  cruiser  at  anchor  in  Ely  Bay,  as  to 
cause  the  vessel  to  fairly  reel  by  the  concussion.* 
Her  Majesty’s  ship  Southampton^  of  fifty  guqs,  ex¬ 
perienced  a  heavy  storm  of  lightning  and  thunder 
on  the  30th  of  June,  1842,  on  the  coast  of  South 


*  Mayo  Constitution, 


DISRUPTIVE  DISCHARGE. 


'73 


America,  when  a  heavy  electrical  discharge  fell  so 
close  to  the  ship,  that  it  appeared  to  strike  the  main- 
chains.* 

During  the  passage  of  Her  Majesty’s  ship  Van¬ 
guard^  of  eighty  guns,  from 'Portsmouth  to  the  Med¬ 
iterranean,  in  1840,  a  dense  explosion  of  lightning 
fell  close  upon  the  ship’s  quarter,  without  aliecting 
the  masts.f 

The  Dart  steam-packet,  whilst  on  her  passage 
from  London  to  Margate,  in  July,  1829,  was  exposed 
to  a  severe  thunderstorm  about  five  miles  below  the 
Nore.  The  electrical  discharge  struck  the  sea  so 
near  the  vessel  as  to  shake  her  considerably.  One 
of  the  passengers  stated  that  he  saw  a  ball  of  fire  fall 
into  the  water  about  twenty  feet  from  the  larboard 
side  of  the  ship.:]; 

A  great  number  of  instances  of  this  kind  might 
be  adduced  in  support  of  this  important  fact ;  it  is 
however  unnecessary  to  go  at  present  into  any  fur¬ 
ther  detail.  We  will  therefore  pass  on  to  the  track 
of  the  discharge,  supposing  it  to  be  determined  in 
the  direction  of  the  masts;  and  with  a  view  of  sim¬ 
plifying  the  question,  we  will  select  a  common  case 
in  which  it  falls  on  one  mast  only,  viz.,  on  the  main¬ 
mast,  in  the  direction  ah  f'S  (fig.  10).  In  pursuing 
this  course,  the  same  general  principle  is  apparent, 
i.  e.,  the  electrical  discharge  is  observed  to  fall  on  all 
those  bodies  which  tend  to  assist  its  progress,  and 
which  happen  to  occupy  certain  relative  positions, 

*  Master’s  log.  f  Extract  from  private  letter. 

\  Report  of  CoJnmission  on  Shipwreck  by  Lightning,  p.  84. 

4 


74 


OBSERVED  EFFECTS  ON 


and  upon  no  others :  attacking  witk  destructive  vio¬ 
lence,  imperfect  conducting  matter,  and  producing  in 
various  insulators,  intermediate  between  good  con¬ 
ductors,  all  the  effects  of  a  powerful  expansive  force. 
If  we  examine  the  course  of  any  discharge  of  light¬ 
ning,  through  a  building  or  a  ship,  we  shall  find  this 
effect  invariable.  The  damage  has  always  ensued 
where  good  conductors  cease  to  be  continued,  and 
the  destructive  effects  most  apparent,  are  those  com¬ 
monly  caused  by  an  expansive  force. 


Observed  Effects  on  Buildings  and  Ships. 

The  damage  done  by  lightning  to  Her  Majesty’s 
ship.  Rodney^  of  ninety  guns,  may  be  adduced  in 
illustration  of  this  result  in  nature.  This  vessel, 
one  of  the  finest  of  our  line-of-battle  ships  in  the 
Mediterranean,  was  struck  by  lightning  on  the  6th 
of  December,  1838,  off  the  south-east  coast  of  Sicily, 
at  9  A.  M.  The  electrical  discharge  fell  on  the  vane- 
spindle,  which  was  of  wood,  and  on  the  truck  at  the 
mast-head.  It  then  glanced  over  the  royal  pole  to 
the  head  of  the  top-gallant  mast,  probably  assisted 
by  the  moisture  on  its  surface  (p.  48) ;  here  it  fell  on 
a  copper  funnel,  sixteen  inches  long  and  ten  inches 
in  diameter,  placed  on  the  mast  for  the  support  of 
the  rigging.  The  resistance  through  the  air,  over 
the  surface  of  the  mast,  seems  to  have  been  greater 
than  through  the  wood  ;  hence  the  top-gallant  mast 
was  shivered ;  it  now  seized  upon  the  metals  about 


BUILDINGS  AND  SHIPS. 


Y5 


the  head  of  the  topmast,  and  also  on  some  men 
there  on  the  cross-trees.  From  thence  it  struck 
over  the  surface  of  the  topmast  to  the  metallic 
bodies  about  the  parrel  of  the  topsail-yard,  and  so 
passed  saltum  to  the  lower  mast,  leaving  it  in  a 
tottering  state.  The  expansive  elfect  was  so  great, 
that  thirteen  of  the  iron  hoops  were  burst  open  : 
about  seven  feet  above  the  deck  the  concentrated 
shock  divided;  one  portion  passed  over  the  ham¬ 
mock  nettings  into  the  sea ;  a  second  seized  upon  a 
metallic  pump  used  for  washing  decks,  and  passed 
along  the  course  of  it  through  the  ship’s  side,  a  third 
division  passed  below  to  the  orlop  deck,  and  through 
the  metallic  bodies  in  the  hull,  leaving  the  ship  be¬ 
tween  decks  full  of  a  sulphurous  odor  and  an  ap¬ 
parent  smoke.  In  this  course,  the  discharge  evi¬ 
dently  sought  assistance  from  all  the  conducting 
matter  it  could  find,  viz.,  wet  ropes,  copper  funnel 
for  rigging,  iron  work,  &c.,  about  the  topmast  cap, 
men  on  the  cross-trees,  metallic  bodies  about  the 
parrel  of  the  topsail-yard,  &c.  ;  and  between  all 
these  it  produced  destructive  effects.  The  inter¬ 
rupted  circuit  is  quite  evident  in  this  case.  It  is 
traceable,  first,  to  the  copper  funnel ;  secondly,  from 
thence  to  the  conducting  bodies  at  the  heel  of  the 
top-gallant  mast ;  thirdly,  from  thence  to  the  metallic 
masses  about  the  yard ;  fourthly,  between  this  and 
the  head  of  the  lower  mast ;  fifthly,  from  this  point 
over  the  iron  hoops  on  the  lower  mast;  lastly,  to 
the  hull  and  sea.  The  circumstance  of  the  dis¬ 
charge  striking  over  some  portions  of  the  mast  with- 


76  ST.  martin’s  church 

out  damage,  is  quite  in  accordance  with  all  the 
known  laws  of  electrical  action  already  described 
(p.  48) ;  thus  a  trace  of  water  will  allow  a  highly- 
charged  jar  to  explode  over  a  slip  of  glass  without 
damage;  and  Dr.  Franklin  found  he  could  not  de¬ 
stroy  a  wet  rat  by  artificial  electricity,  although  he 
could  a  dry  one,  in  consequence  of  the  moisture 
conducting  the  charge  over  the  surface  of  the  body. 

The  following  cases  of  damage  by  lightning, 
which  have  recently  occurred  in  London  are  worthy 
of  attentive  consideration,  inasmuch  as  the  facts  are 
still  present  to  us,  and  the  evidence  they  furnish 
of  the  course  of  electrical  discharges  is  very  com¬ 
plete.  They  have  therefore  been  somewhat  mi- , 
nutely  described. 

Sl  Martinis  Churchy  struck  by  Liglitnwg^  2^th  July^ 

1842. 

Before  tracing  the  course  of  the  electrical  dis¬ 
charge  through  the  tower  of  this  beautiful  building, 
it  will  be  requisite  briefly  to  notice  the  position  of 
the  various  rooms  and  substances  through  which  it 
passed,  together  with  such  other  circumstances  as 
bear  immediately  on  the  great  points  under  con¬ 
sideration. 

A  section  of  this  tower  is  given  in  figs.  11  and  12. 
The  spire,  s  c  A,  terminates  in  an  iron  rod,  c  A,  formed 
into  a  spindle  at  its  extreme  point,  for  the  support 
of  the  vane,  A.  This  rod  is  from  four  inches  and  a 
half  to  five  inches  square,  and  about  twenty-seven 


STRUCK  BY  LIGHTNING. 


feet  in  length.  It  projects  about  twelve  feet  into 
the  air,  and  passes  fifteen  feet  into  the  spire  through 
a  gilded  ball  of  copper,  thirty-three  inches  in  diame¬ 
ter,  and  one-sixteenth  of  an  inch  thick,  and  through 
two  solid  blocks  of  stone.  It  is  supported  within  by 
a  strong  cross  of  iron,  let  into  the  masonry  at  c  (fig. 
11).  The  weight  of  the  bar  is  about  twelve  cwt. 
and  three-quarters,  and  its  extreme  point  about  two 
hundred  feet  from  the  ground.  There  are  other 
iron  crosses  in  the  interior  of  the  spire,  besides  that 
supporting  the  spindle  of  the  vane,  as  at  t  and  v  (fig. 
11):  these  serve  as  cramps  to  the  masonry ;  they  are 
not  connected  with  each  other.  The  vane  at  A  is 
constructed  of  sheet  copper,  well  gilded,  and  is 
about  eight  feet  long  and  six  feet  wide. 

The  spire  is  a  light  hollow  structure,  forty -four 
feet  high,  standing  on  an  open  cupola,  and  sur¬ 
rounded  by  ornamental  columns  and  arches.  The 
floor  of  this  cupola  is  covered  with  lead,  and  there 
is  a  massive  framework  of  wood  and  iron,  resting 
on  it.  This  frame  is  constructed  in  two  parts,  for 
the  support  of  a  flagstaff  F,  one  of  which  can  be 
pushed  out  clear  of  the  tower  when  required.  Be¬ 
neath  the  cupola  is  the  dial-room  /  containing  the 
iron  spindles  of  the  clock  faces,  as  at  e  /  n.  The 
figures  marking  the  hours  constitute  portions  of  the 
stone-facing  which  surrounds  the  recesses  of  the 
circles  forming  the  centre  of  the  dials:  these 
circles  are  formed  of  shutters  of  wood  and  iron, 
in  eight  divisions,  and  are  painted  black.  The 
four  cross  rods  ate/ (fig.  12,)  carry  the  hour  and 


*78  ST.  martin’s  church 

Fio.  11,  Fig.  12. 


STRUCK  BY  LIGHTNING. 


79 


minute  hands  of  each  dial,  and  are  supported  in 
the  middle  of  the  dial-room  yj  without  touching 
the  walls. 

Under  the  dial-room  is  the  belfrv  B,  in  which  are 
the  bells,  suspended  in  frames  in  the  usual  way ; 
they  weigh  from  five  to  thirty-one  cwt.  Beneath  the 
belfry  is  the  clock-room  a  ;  the  clock  in  this  room 
is  supported  in  a  massive  iron  frame  fixed  to  the 
floor ;  an  iron  rod  /  G,  about  three-fourths  of  an 
inch  in  diameter,  and  forty-six  feet  long,  passes  from 
the  wheel-work  up  through  the  belfry  B  to  the 
spindles  at/  by  which  the  requisite  motion  is  con¬ 
veyed  to  the  hands  on  the  dial-  plates  ;  this  rod  is 
constructed  of  several  pieces,  united  by  brass  screws  : 
it  is  cased  in  wood,  and  passes  within  ten  inches  of 
the  lip  of  each  bell. 

Beneath  the  clock-room  is  the  ringing-chamber 
R,  having  windows  w  w'  with  iron  frames ;  imme¬ 
diately  without  these  is  the  lead,  covering  the  roof 
of  the  church,  as  at  M. 

We  have  now  before  us  almost  every  particular 
requisite*to  a  clear  comprehension  of  the  track,  and 
phenomena  of  the  electrical  explosion  which  fell  on 
this  fine  structure. 

The  first  point  struck  was  the  point  of  the  vane- 
spindle  at  A ;  the  discharge  passed  into  the  spire 
through  the  rod  A  c,  without  any  damage  to  the 
blocks  of  stone  immediately  surrounding  it,  and 
without  affecting  the  copper  ball  or  the  gilding  of 
the  vane.  The  only  effect  produced  was  the  dis¬ 
turbance  of  a  little  cement  about  the  ball,  which 


80 


ST.  martin’s  church 


seemed  as  if  shaken  by  a  violent  concussion  of  the 
air.  At  the  cross  c  the  discharge  left  the  vane-rod, 
and  passed  into  the  masonry  of  the  spire,  starting 
an  angle  stone,  and  from  thence  so  damaged  the 
spire  in  passing  down  it,  as  to  leave  the  whole  in  a 
tottering  state.  Two  blocks  of  stone  were  thrown 
completely  out  of  their  places,  and  fell  through  the 
roof  into  the  church,  the  j  bints  of  the  spire  were 
all  loosened,  and  its  general  surface  contorted.  Two 
other  stones  were  quite  dislocated  ;  if  these  had  also 
been  thrown  out,  the  whole  of  the  upper  portion  of 
the  spire  must  have  fallen.  From  the  base  of  the 
spire,  the  discharge  fell  with  destructive  violence 
upon  the  frame-work  of  the  flagstaff  at  c?,  the  wood¬ 
work  of  which  was  shivered,  and  then  seizing  the 
lead  floor  of  the  cupola,  it  forced  a  passage  to  a 
metal  clamp  within  the  masonry,  where  it  tore  up 
and  fractured  a  large  flat  stone,  and  turned  it  com¬ 
pletely  over ;  in  this  way  it  passed  to  the  nearest 
points  outside  the  tower  leading  to  the  north  and 
west  dials:  upon  these  the  discharge  divided,  and 
fell  upon  the  gilded  letters  xi.  and  xii.,  the  gold  of 
which,  on  the  west  dial  more  especially,  was  burnt 
up  and  blackened.  From  these  points  it  exploded 
upon  the  minute-hands;  here  it -also  blackened  the 
gold,  and  damaged  the  points  of  the  hands.  From 
this,  it  passed  along  the  spindles  of  the  north  and 
west  dials  into  the  dial-room,  without  affecting  the 
surrounding  parts,  and  seizing  the  iron  rod /g,  con¬ 
necting  the  spindles  with  the  clock,  it  passed  safely 
within  its  case  of  wood,  and  between  the  masses  of 


STRUCK  BY  LIGHTNING. 


81 


metal  in  the  bells  down  to  the  works  of  the  clock : 
the  only  traces  left  in  this  course,  were  a  little  fusion 
of  the  brass  screws,  and  of  the  iron  at  the  union  of 
the  joints.  The  discharge,  on  reaching  the  works 
of  the  clock,  melted  a  small  copper  wire  by  which 
the  lever  handle  key  was  suspended  on  the  iron 
frame :  it  now  spread  over  the  wheels  and  other 
parts,  magnetized  the  steel  pivots,  blackened  the 
silver  face  of  the  regulator,  and  burst  open  the  door 
of  the  outer  wooden  casing, — it  did  not,  however, 
stop  the  clock.  The  discharge,  on  leaving  these 
conductors,  forced  a  passage  through  the  floor  of  the 
clock-room  G  by  the  assistance  of  some  metal  clamps, 
into  the  ringing  chamber  R,  leaving  the  floor  as  if 
blown  up  by  gunpowder.*  Coming  out  just  over 
one  of  the  iron  window-frames  w,  it  shattered  all 
the  glass  in  the  window  by  the  violent  concussion, 
and  left  marks  of  fusion  on  small  streaks  of  lead  in 
the  joints  of  the  stones.  By  this  course  it  reached 
the  lead  of  the  roof  at  M,  and  slightly  fused  it  at  the 
point  on  which  the  discharge  first  fell.  After  this 
it  became  dispersed  upon  the  earth  without  further 
damage,  by  the  large  masses  of  metal  and  pipes  con¬ 
necting  the  roof  with  the  ground. 

It  is  impossible  to  conceive  a  case  giving  a  better 
insight  into  the  nature  of  disruptive  discharges, 
through  a  fortuitous  arrangement  of  good  and  im¬ 
perfect  conductors,  than  this  now  before  us.  In  the 
first  place,  we  may  observe  that  all  the  damage  has 
occurred  in  points  where  good  conducting  matter 

ceases  to  be  continued, — as  for  example,  between 
4^ 


82  ST.  martin’s  church  struck  by  lightning. 

the  termination  of  the  vane-rod  at  c  and  the  clock- 
faces  at  c  and^  and  again  between  the  works  of  the 
clock  at  G  and  the  lead  of  the  roof  at  M,  whilst  the 
course  of  the  discharge  in  the  irregular  line  A.cs  def 
BGWM,  is  so  marked  and  definite,  and  so  inde¬ 
pendent  of  bodies  not  contributing  to  assist  its  pro¬ 
gress,  that  we  perceive  it  actually  passing  down  the 
small  iron  rod  f  G  within  a  few  inches  of  the  bells, 
without  affecting  in  any  way  these  large  metallic 
masses,  or  disturbing  the  wooden  case  by  which  the 
rod  was  surrounded.  The  discharge  in  passing  upon 
the  dials,  selected  the  north  and  west  faces  as  afford¬ 
ing  the  easiest  line  of  transit,  and  as  the  minute 
hands  only  could  contribute  to  the  conduction,  being 
at  the  time  in  a  position  to  transmit  it  to  the  centre 
of  the  dial,  these  only  were  affected ;  the  hour  hands, 
although  in  continuation  with  the  lower  part  of  the 
dials,  were  evidently  without  the  line  of  action:  the 
course  of  the  discharge,  therefore,  became  diverted 
at  right  angles  nearly  from  the  line  of  the  hands  in 
order  to  pass  upon  the  line  of  metals  within  the 
tower,  thus  completely  coinciding  with  the  phe¬ 
nomena  of  artificial  discharge.* 

*  Every  care  has  been  taken  to  verify  the  facts  of  this  case, 
Mr.  Watkins,  Optician,  Charing  Cross,  London,  well  known  as  a 
careful  observer  of  such  phenomena,  made  a  personal  observation 
of  the  spire  soon  after  the  lightning  fell  on  it,  and  very  kindly 
furnished  the  result  of  his  inquiries,  Mr.  E..  Dyer,  of  the  hTorfolk 
Hotel,  Surrey-street,  also  devoted  much  attention  to  the  subject, 
and  obtained  from  those  immediately  connected  with  the  church 
every  particular  that  could  be  desired.  Mr.  Newberry,  the  steeple- 
keeper,  Mr.  Hennings,  the  builder,  and  Mr.  Langstaffe,  who  re- 


BRIXTON  CHURCH  STRUCK  BY  LIGHTNING. 


83 


Brixton  Churchy  struck  hy  Lightning^  24:th  Aprils  1842. 

The  course  of  this  discharge  is  traced  in  fig.  13, 
which  represents  a  section  of  the  tower.  There  is  a 
metallic  cross  V  on  the  summit  of  the  dome;  this 
cross  is  of  sheet  copper,  four  and  a  half  feet  in  height, 
and  five  inches  square,  and  is  supported  by  an  iron 
bar,  which  passes  within  the  cross  through  the 
masonry  of  the  dome,  and  is  secured  by  a  nut  at  N. 
The  masonry  of  the  dome  is  very  massive,  and  the 
joints  of  the  stonework  are  strengthened  by  lead 
solderings.  The  dome  is  supported  by  stone  columns 
about  twelve  feet  high,  as  at  M.  Immediately  under 
the  cupola  is  the  clock-room  c,  the  roof  of  which  is 
of  wood  covered  with  lead ;  c  is  the  position  of  the 
clock:  the  works  communicate  with  the  diabplates 
by  means  of  iron  rods,  as  D  c  half  an  inch  in  diame¬ 
ter.  D  is  the  position  of  one  of  the  four  clock-faces; 
the  dial-plates  are  of  sheet  copper,  about  four  feet  in 
diameter,  and  the  figures  for  the  hours,  &c.,  are 
covered  with  leaf  gold.  The  works  of  the  clock 
communicate  with  two  bells  at  B  by  a  small  iron 
wire  about  thirty  feet  long,  and  one-tenth  of  an  inch 
in  diameter ;  this  wire  is  not  continuous,  but  made 
up  of  several  pieces  looped  together ;  it  is  supported 
by  means  of  small  staples  against  an  upright  of  wood. 
The  bells  at  b  are  very  close  to  each  other :  they  are 


gilt  the  vane,  (fee.,  gave  freely  all  the  information  in  their  power. 
T.  Morris,  Esq.  architect,  also  contributed  much  valuable  infor¬ 
mation. 


84 


BRIXTON  CHURCH 


quite  clear  of  the  walls  and  the  floor,  and  the  larger 
one  is  always  in  connection  with  the  clock  by  the 
wire  /  — in  fact,  the  striking  weight  rests  on  it, 
being  raised  by  the  wire  to  strike  the  hour.  Beneath 

Fig,  13. 


the  belfry  b  is  a  room  E  communicating  with  it  by  a 
trap ;  there  is  an  iron  clamp,  ^,  under  the  floor,  about  . 
fifteen  inches  from  the  bell,  and  immediately  outside, 


STRUCK  BY  LIGHTNING. 


85 


at  about  a  foot  distant,  is  the  base  of  one  of  the  orna¬ 
mental  columns  T,  which  surround  the  middle  portion 
of  the  tower.  There  are  sixteen  of  these  columns, 
and  they  are  about  eighteen  feet  long.  At  the  base 
of  column  T  is  the  lead- work  m  descending  over  the 
roof,  and  connected  with  the  earth  by  metallic  gutters 
and  pipes.  On  reviewing  the  position  of  these  differ¬ 
ent  parts,  we  cannot  but  be  struck  with  the  analogy 
in  their  electrical  relation  to  similar  parts  in  St. 
Martin’s  spire,  just  described;  we  should  according¬ 
ly  expect  to  find  precisely  similar  effects,  and  such  is 
really  the  case,  the  course  of  the  discharge  being  as 
follows. 

The  explosion  fell  first  on  the  cross  V,  and  follow¬ 
ed  it  down  to  the  masonry  of  the  dome ;  there  it 
diverged  and  rent  the  dome  completely  open,  then 
finding  its  way  along  the  inner  side  of  one  of  the 
columns  M,  it  slightly  damaged  the  stone- work  in  the 
vicinity.  It  now  reached  the  metals  on  the  dials, 
and  passed  to  the  works  of  the  clock  at  c  by  the  iron 
rods  D  c,  and  from  thence  along  the  wire  and  wooden 
upright  ft  to  the  bell  B  ;  this  wire  was  knocked  to 
pieces,  and  portions  of  it  dissipated.  From  the  ter¬ 
mination  of  the  wire  it  burst  upon  the  floor  and 
clamp  at  f,  as  the  shortest  and  easiest  course  to  the 
lead  m  on  the  roof  of  the  church.  Exploding  upon 
this  point,  it  produced,  by  a  common  law  of  electrical 
action,  so  much  expansion  as  to  shatter  the  base  of 
the  column  t;  the  wood  of  the  floor  also  at  the 
clamp  i  was  torn  up,  as  in  St.  Martin’s  spire,  but 
with  less  damage ;  after  this  the  discharge  found  its 


80 


8T.  bride’s  church 


way  to  the  earth,  with  but  little  further  difficulty. 
The  interrupted  circuit  traceable  here,  is  represented 
by  the  irregular  line  V  w  M  D  c/^  T,  &c.,  and  the  dis¬ 
ruptive  discharge  is  precisely  of  the  same  character 
and  description  as  that  just  described  (p.  82).* 

In  every  instance  of  damage  to  buildings  or  ship¬ 
ping  by  lightning,  the  course  of  the  electrical  dis¬ 
charge  is  determined  in  a  similar  way,  through  points 
presenting  the  least  resistance  to  its  progress,  and  the 
mischief  invariably  occurs  between  detached  masses 
of  metal.  The  beautiful  steeple  of  St.  Bride’s  Church 
in  London,  struck  by  lightning  in  June,  1764,  fur¬ 
nishes  a  most  remarkable  instance  of  this.  The  spire 
of  this  steeple,  where  it  rises  above  the  belfry,  is 
composed  of  four  stories  of  different  orders  of  archi¬ 
tecture,  beside  the  obelisk  immediately  over  them. 
The  stone  piers  of  these  stories  are  connected  together 
and  strengthened  by  horizontal  iron  bars;  near  the 
height  of  the  capital  of  the  pilasters,  each  story  has  a 
set  of  four  bars,  placed  crosswise,  and  tied  together 
by  chain  bars  within  the  stone  work.  The  obelisk 


*  The  facts  connected  with  this  cas^  have  been  minutely  detail¬ 
ed  by  Mr.  C.  V.  Walker,  and  there  is  not  the  slightest  doubt  of  their 
accuracy.  It  is,  however,  proper  to  observe,  that  in  the  account 
given  by  Mr.  Walker,  he  supposes  a  great  portion  of  the  charge  to 
have  passed  outside  the  building  by  an  iron  pipe,  because  the 
damage  done  at  the  point  %  was  not,  he  thinks,  adequate  to  the 
force  of  the  shock  as  experienced  at  the  base  of  the  column  t.  This 
supposition,  however,  is  not  warranted  by  any  trace  of  the  discharge 
in  the  direction  Mr.  Walker  has  pointed  out,  and  must,  therefore,  be 
so  far  regarded  as  hypothetical.  His  account  of  this  case,  however, 
is  singularly  clear  and  instructive. 


STRUCK  BY  LIGHTNING. 


87 


terminates  in  seven  courses  of  stone,  the  five  upper 
ones  being  connected  together  at  the  top  and  bottom 
by  iron  collars  soldered  with  lead.  An  iron  bar, 
about  twenty  feet  in  length  and  two  inches  square, 
passes  through  these  for  about  ten  feet  in  a  groove 
cut  through  the  middle  of  the  solid  stones  and 
filled  in  with  lead.  This  bar  rests  in  the  two  solid 
stones  of  the  lower  courses,  in  which  it  is  sunk 
five  inches  deep,  and  is  further  secured  by  melted 
lead.  The  upper  part  of  the  bar  is  cylindrical, 
and  covered  for  about  ten  feet  by  a  ball  and  cross, 
and  by  a  vane,  all  of  gilded  copper.  To  lessen  the 
quantity  of  stone  in  this  beautiful  structure,  cramps 
of  iron  are  employed  in  several  places,  on  which 
ornamental  stones  are  placed.  Other  iron  bars  are 
also  employed  to  support  the  top  of  the  windows,  so 
that  a  more  complete  series  of  discontinuous  metallic 
bodies  intermixed  with  imperfect  conducting  matter, 
cannot  well  be  conceived. 

When  the  lightning  struck  this  steeple,  it  made 
successive  leaps  between  these  metallic  bodies,  rend¬ 
ing  and  tearing  up  the  masonry  at  the  points  where  it 
entered  and  again  left  them ;  so  that  it  was  requisite 
to  rebuild  eighty-five  feet  of  the  spire.  One  of  the 
iron  bars  in  the  composite  story  was  found  broken 
in  two,  and  another  bent  to  an  angle  of  nearly  forty- 
five  degrees.  'No  damage  whatever  was  done  to  the 
iron  spindle,  the  vane  or  cross,  or  to  the  solid  stones 
through  which  the  iron  bar  passed.  The  gilding  on 
the  top  of  the  cross,  at  the  place  where  the  discharge 
first  struck,  was  the  only  part  affected ;  this  was 


88  ST.  bride’s  church  struck  by  lightning. 

either  dissipated  or  discolored:  a  little  solder  also 
was  melted  at  this  spot,  which  appeared  as  if  acted 
on  by  fire.  The  lightning,  it  is  clear,  entered  here 
upon  the  whole  metallic  mass,  and  was  quietly  con¬ 
ducted  to  the  termination  of  the  iron  spindle  in  the 
two  lower  courses  of  stone  :  its  destructive  operation 
now  commenced,  and  the  destruction  was  repeated 
at  each  successive  leap  between  the  disconnected 
metallic  substances  employed  in  the  construction 
of  the  spire.  The  last  trace  of  it  was  at  the  west 
window  of  the  belfry,  from  whence  it  appears  to 
have  found  an  adequate  conduction  to  the  earth.* 

Before  concluding  these  notices,  it  may  not  be 
unimportant  to  detail,  briefly,  two  cases  of  damage 
by  lightning  which  exhibit  in  a  remarkable  way  its 
destructive  effects  at  sea  and  on  shore,  and  show  still 
further,  the  absolute  necessity  of  guarding  against 
them. 

The  frontispiece  represents  the  condition  of  the 
Thisbe^  an  English  frigate,  struck  by  lightning  in 
January  1786,  near  the  Scilly  Isles,  during  her  pas¬ 
sage  from  Lisbon  to  England.  The  weather  at  the 
time  was  tempestuous  and  squally,  with  showers  of 
hail,  so  that  the  ship  was  hove-to  under  storm  stay¬ 
sails,  f  The  electrical  discharge,  after  disabling  seve¬ 
ral  of  the  crew,  struck  on  the  mainmast,  and  set  the 
sails  and  rigging  on  fire :  it  also  struck  the  foremast 
and  shivered  it.  ^  To  get  clear  of  the  burning  mass,' 


*  Phil.  Trans,  for  1'764,  pp.  201  and  227. 
f  Ship’s  log.  \  Idem. 


NATURE  OF  LIGHTNING  RODS. 


89 


the  master  cut  one  of  the  lanyards  of  the  main 
shrouds  to  windward,  when  the  force  of  the  gale 
carried  the  whole  over  the  side,  together  with  the 
mizen-topmast ;  the  fore-topmast  soon  followed,  so 
that .  the  ship  was  left  almost  a  total  wreck.  The 
electrical  discharge  knocked  down  several  of  the 
crew  near  the  guns,  and  swept  the  decks.  * 


PEACTICAL  EESULT  OF  THE  PEECEDING 

INQUIEIES. 

Nature  of  Lightning  Rods. 

The  damage  sustained  by  buildings  and  ships  in 
thunderstorms  being  invariably  found  to  occur  in 
the  spaces  where  good  conductors  of  electricity  cease 
to  be  continued,  it  became  an  important  question  in 
practical  science,  how  far  it  would  be  desirable  to 
provide  at  once  a  continuous  line  of  conduction, 
through  which  the  electrical  discharge  might  be  trans¬ 
mitted  without  any  intermediate  explosion,  and  con¬ 
sequently  without  damage  to  the  general  mass.  An 
idea  first  suggested  by  the  American  philosopher. 


*  A  similar  result  ensued  in  the  Lowestoffe,  a  sister  ship,  in  the 
Mediterranean,  in  I'JQG.  This  frigate  was  also  dismasted,  and  left 
a  mere  wreck. 


90 


NATURE  OF  LIGHTNING  RODS. 


Franklin,  and  since  carried  effectually  into  practice 
under  the  form  of  a  lightning  rod. 

The  application  of  such  a  rod  to  a  building  or 
ship,  is  evidently  equivalent  to  the  uniting  into  a 
continuous  conducting  train,  all  the  detached  metallic 
masses  between  which  damage  ensues,  and  in  the 
case  of  particular  buildings,  into  the  construction  of 
which  such  masses  do  not  enter,  it  supplies  the  de¬ 
gree  of  conducting  power  requisite  for  their  safety. 
A  conducting  rod,  therefore,  in  whatever  way  it  may 
be  applied,  is  to  be  considered  merely  as  a  means  of 
perfecting  the  conducting  power  of  the  whole  mass, 
so  as  to  admit  of  intense  discharges  of  lightning  being 
securely  transmitted,  which  otherwise  would  not  pass 
without  intermediate  explosion  and  damage ;  for  it 
must  never  be  forgotten,  as  an  important  feature  in 
the  consideration  of  this  question,  that  the  materials 
of  which  buildings  and  ships  are  composed,  are  for 
'the  most  part  such  as  come  under  the  denomination 
of  conductors  (p.  8) ;  the  whole  fabric  is,  therefore, 
to  a  greater  or  less  extent,  an  electrical  conductor. 
Now  the  chance  of  its  escaping  damage  from  a  dis¬ 
charge  of  lightning,  increases  with  its  power  of  trans¬ 
mitting  the  electrical  action  by  which  it  is  assailed. 
If  we  could  suppose  a  ship  or  building  to  have  a 
perfect  conducting  powder  in  all  its  parts,  or  if  we 
imagine  it  to  be  metallic  throughout,  then  damage 
from  lightning  would  be  unknown.  Thus  discharges 
of  lightning  struck  repeatedlj^  on  the  iron  steamboat 
which  accompanied  Lander  in  his  last  attempt  to  ex¬ 
plore  the  interior  of  Africa,  without  producing  the 


NATURE  OF  LIGHTNING  RODS. 


91 


sliglitest  effect  on  it ;  whilst  vessels  built  of  wood 
and  metal  were  damaged.  A  man  in  armor  would 
certainly  be  safe  in  a  thunderstorm,  from  the  great 
conducting  power  of  the  metal  as  compared  with  the 
human  body.  The  great  object,  therefore,  to  be  at¬ 
tained  in  the  application  of  lightning  conductors  to 
the  defence  of  buildings  and  shipping  from  lightning, 
is  to  bring  the  general  mass  as  nearly  into  this  state 
as  possible. 

It  has  already  been  observed  (p.  9),  that  Mr.  Cav¬ 
endish  determined  the  conducting  power  of  iron  to 
be,  in  relation  to  that  of  water,  as  four  hundred  mil¬ 
lions  to  one»  Taking  therefore  the  conducting  power 
of  water  as  unity,  and  assuming  it  as  the  value  of 
the  mean  conducting  power  of  the  general  mass  of  a 
building,  which  is  upon  the  whole  not  far  from  the 
truth,  then,  by  giving  a  building  a  lightning  conduc¬ 
tor  of  great  capacity,  and  connecting  it  with  the  de¬ 
tached  masses  of  metal  as  far  as  is  possible,  we  mul¬ 
tiply  its  chance  of  escaping  damage,  in  the  interme¬ 
diate  points  in  which  the  conductor  is  applied,  four 
hundred  millions  of  times  ;  and  considering  that  by 
the  laws  of  electrical  action,  the  electrical  discharge 
finds  its  way  through  any  line  or  lines,  which  upon  the 
whole  offer  the  least  resistance  to  its  passage,  nothing 
can  be  clearer  than  the  deduction,  that  any  incapa¬ 
city  of  the  buildiug  as  a  whole,  to  transmit  the  charge 
through  its  parts  without  explosion,  would  be  sup¬ 
plied  by  the  presence  of  the  conductor ;  and  hence 
this  multiplied  chance  of  escape  applies  equally  to 
the  whole  building.  It  is  therefore  demonstrable  by 


92  LAWS  OF  ELECTKICAL  CONDUCTION. 

physical  facts,  that  perfect  security  is  to  be  derived 
from  an  efficient  conductor  properly  applied. 

The  first  lightning  conductor  seen  in  England, 
was  erected  by  Dr.  Watson  at  Payneshill,  in  1762. 
In  1769  the  Jacob  tower  at  Hamburg  was  defended 
by  a  lightning  rod,  and  after  the  cathedral  church  at 
Sienna  had  been  repeatedly  damaged  by  lightning,  a 
similar  means  of  protection  was  employed  there  also. 
The  inhabitants  at  first  regarded  the  rod  with  terror 
and  apprehension,  and  called  it  a  Heretic„JSpd ;  but 
on  the  10th  of  April,  1777,  a  thunderstorm  occurred, 
and  there  fell  on  the  tower  a  heavy  stroke  of  light¬ 
ning,  which  was  carried  off  by  the  rod,’  without 
doing  the  slightest  damage  even  to  the  gilded  orna¬ 
ments  near  which  it  passed.'^  The  inhabitants  now 
began  to  look  on  the  heretic  rod  with  more  confi¬ 
dence  ;  and  it  is  an  important  fact,  that  this  church 
does  not  seem  to  have  suffered  from  lightning  since. 

Laws  of  Electrical  Conduction, 

The  heating  effect  of  the  same,  or  different  quan¬ 
tities  of  electricity,  on  metallic  wires  of  the  same  or 
different  diameters,  is  as  the  square  of  the  passing 
quantity  of  electricity  directly,  and  as  the  square  of 
the  diameter  of  the  wire  inversely.  Thus  the  heat 
developed  by  a  passing  shock  is  four  times  as  great 
when  the  quantity  of  electricity  is  doubled,  and  only 
one-fourth  as  great  when  the  diameter  of  the  wire  is 
doubled.  A  metallic  rod,  therefore,  of  twice  the  di- 


*  Marbuch,  Enhyklopmdie,  vol.  i.,  p.  314. 


LAWS  OF  ELECTRICAL  CONDUCTION. 


93 


ameter,  conducts  twice  the  quantity  of  electricity 
with  the  same  development  of  heat.  Taking  the 
heat  evolved  as  proportionate  to  the  resistance,  we 
may  conclude,  that  the  conducting  power  of  a  me¬ 
tallic  body  varies  with  the  area  exposed  in  cutting  it 
transversely  to  its  length ;  that  is  to  say,  with  the 
area  of  its  section,  since  this  is  proportionate  to  its 
solid  contents. 

In  estimating  the  resistance  of  a  metallic  body 
to  the  transmission  of  a  shock  of  electricity,  we  have 
also  to  take  into  consideration  the  distance  traversed. 
Now  the  resistance  to  electrical  transmission  through 
a  metallic  wire,  has  been  found  to  increase  with  the 
length  of  the  wire ;  that  is  to  say,  the  resistance  to 
the  transmission  of  the  charge  was  twice  as  great 
when  the  length  of  the  conductor  was  doubled ;  a 
law  observable  from  one  hundred  up  to  one  thousand 
feet  in  length.  A  lightning  conductor,  therefore, 
should  have  its  dimensions  increased,  when  required 
to  be  of  considerable  extent. 

The  explanation  of  the  above  general  laws  seems 
to  be  this  :  supposing  a  given  quantity  of  electricity 
to  fall  on  a  single  metallic  particle,  and  to  experience 
a  given  resistance  to  its  progress,  then  this  resistance 
would  be  diminished  by  placing  a  second  particle 
by  the  side  .of  it,  for  the  charge  would  be  divided 
between  the  two.  If  two  other  particles  were  added, 
we  may  conceive  it  to  be  still  further  reduced  in  pro¬ 
portion  to  the  number  of  particles  sharing  in  the 
conduction.  Now,  in  the  case  of  the  section  of  a 
metallic  wire,  the  diameter  of  which  is  double  that 


94 


MECHANICAL  EFFECTS  OF 


of  another,  there  are  four  times  the  number  of  par¬ 
ticles, — hence  the  resistance  with  the  same  quantity 
of  charge  is  reduced  to  one-fourth.  In-a  similar  way 
it  may  be  shown,  that  by  increasing  the  length  of 
the  conductor,  we  continually  increase  the  number 
of  particles  to  be  passed  through, — hence  the  resist¬ 
ance  through  twice  the  length  will  be  twice  as  great, 
through  three  times  the  length  three  times  as  great, 
and  so  on.  In  the  case  of  the  quantity  of  electricity 
being  increased,  we  have  the  resistance  dependent 
not  only  on  the  increased  charge,  but  also  on  its  in¬ 
creased  force.  Thus  a  particle  of  metal  conducting 
a  double  quantity  of  electricity  is  subject  to  a  double 
force,  since  it  is  quite  reasonable  to  conclude  that 
the  forces  (p.  17)  with  which  the  opposite  electrical 
powers  tend  to  unite,  would  increase  with  the  amount 
of  disturbance. 


Mechanical  Effects  of  the  Electrical  Discharge. 

But  it  is  not  only  the  heating  effect  of  the  dis¬ 
charge  we  have  to  consider ;  it  is  necessary  to  take  also 
into  the  account  its  more  mechanical  effects, — indeed, 
it  is  the  expansive  action  which  produces  the  great 
mass  of  damage  by  lightning  so  commonly  observed. 
If  a  powerful  shock  of  electricity  be  transmitted  by 
a  fine  wire,  the  wire  will  very  often  appear  crippled 
throughout  its  length,  and  will  exhibit  a  series  of  zig¬ 
zag  creases.  And  if  a  similar  shock  be  passed  be¬ 
tween  two  metallic  balls  in  a  confined  portion  of  air, 
the  air  will  be  caused  to  expand  with  great  violence. 


THE  ELECTRICAL  DISCHARGE. 


95 


SO  as  to  frequently  burst  open  tbe  containing  vessel. 
Light  bodies  such  as  wafers  will  become  dispersed  in 
all  directions,  when  exposed  to  the  expansive  effect 
produced  by  the  electric  shock  in  passing  through  a 
short  interval  of  air. 

At  the  time  the  steeple  of  St.  Bride’s  church, 
London,  was  struck  by  lightning,  in  June,  1764,  it 
is  stated  by  Mr.  Delaval,  F.E.S.,  who  communicated 
a  most  interesting  detail  of  the  circumstances  to  the 
Eoyal  Society,  that  “the  lightning  acted  as  an  elastic 
fluid,”  and- that  “  the  effects  are  exactly  similar  to 
those  which  would  have  been  produced  by  gunpow¬ 
der,  pent  up  in  the  same  places  and  exploded.  A 
stone  weighing  about  seventy  pounds  was  thrown  to 
a  distance  of  fifty  yards ;  an  iron  bar  half  an  inch 
in  thickness,  and  about  two  feet  in  length,  joining 
some  of  the  masonry  of  the  tower,  was  not  only 
broken  in  two,  but  one  part  of  it,  according  to 
Dr.  Watson,*  was  actually  bent  to  an  angle  of 
45°.” 

The  mechanical  effects  of  lightning,  seen  in 
piercing  solid  bodies  with  holes,  in  splitting  them 
in  pieces,  and  in  projecting  their  fragments  (some¬ 
times  of  enormous  weight)  to  great  distances,  are  so 
well  known,  and  so  generally  admitted,  that  it  will 
be  needless  to  multiply  instances  in  proof  of  it ;  but 
a  circumstantial  statement  of  some  remarkable  cases 
of  this  kind  may  throw  light  upon  the  manner  in 
which  the  electric  fluid  acts. 


*  Phil.  Trans,  for  1764. 


9C 


MECHANICAL  EFFECTS  OF 


In  the  autumn  of  1778,  lightning  struck  the  house 
of  Casselli,  an  engineer,  at  Alexandria.  It  did  no 
damage,  bat  pierced  the  panes  of  glass  in  the  windows 
with  several  small  holes  about  the  sixth  of  an  inch  in 
diameter.  Small  cracks  in  the  glass  diverged  from 
these  holes  as  centres. 

In  August,  1777,  lightning  struck  the  steeple  of 
the  parish  churcli  of  St.  Sepulchre  at  Cremona,  broke 
the  iron  cross  which  surmounted  the  tower,  and  pro¬ 
jected  to  a  distance  the  weathercock,  which  revolved 
under  the  cross,  and  which  was  made  of  copper, 
tinned,  and  coated  with  oil-paint. 

This  weathercock  was  found  to  have  been  pierced 
with  eighteen  holes,  nine  of  which  were  very  prom¬ 
inent  on  one  side,  and  the  other  nine  on  the  other. 
As  there  was  no  appearance  of  more  than  one  stroke 
of  lightning,  all  these  holes  must  be  supposed  to 
have  been  pierced  at  once.  The  position  of  the 
holes  are  such  as  would  have  been  produced  by 
blows  imparted  simultaneously  in  opposite  directions 
on  parts  of  the  metal  nearly  contiguous,  and  the  in¬ 
clination  of  the  beards  or  projecting  edges  of  the 
holes  on  one  side  correspond  exactly  with  those  on 
the  other,  the  directions  of  all  the  eighteen  beards 
being  parallel. 

On  the  3d  of  July,  1821,  lightning  struck  a  house 
at  Geneva,  and  pierced  the  tin  which  covered  a  part 
of  the  roof  with  several  holes,  leaving  evident  marks 
of  fusion.  One  piece  of  tin  in  particular,  which 
covered  the  angle  made  by  a  chimney  with  the  sur¬ 
face  of  the  roof  near  it,  was  pierced  with  three  nearly 


THE  ELECTRICAL  DISCHARGE. 


97 


circular  holes,  about  an  inch  and  three  quarters  in 
diameter,  and  about  five  inches  apart,  measured  from 
centre  to  centre.  The  metal  at  the  edges  of  these 
holes  was  bent,  as  it  would  have  been  by  a  force 
bursting  through  it  in  one  direction  or  the  other. 
The  edges  of  the  two  holes  were  bent  on  contrary 
sides. 

On  the  night  between  the  14th  and  15th  of  April, 
1718,  the  church  of  Grouesnon,  near  Brest,  was  struck 
by  lightning  with  such  force  that  it  shook  as  if  by 
an  earthquake.  The  stones  of  the  walls  were  pro¬ 
jected  in  all  directions  to  a  distance  of  from  fifty  to 
sixty  yards. 

The  lightning  which  formally  struck  the  Chateau 
of  Clermont,  in  Beauvoisis,  made  a  hole  twenty-six 
inches  wide  and  the  same  depth  in  the  wall ;  the 
date  of  the  building  of  which  was  so  far  back  as  the 
time  of  Cassar,  and  which  was  so  hard  that  a  pickaxe 
could  with  difficulty  make  any  impression  upon  it. 

On  the  night  between  the  21st  and  22d  of  June,  * 
1723,  lightning  struck  a  tree  in-the  forest  of  Nemours. 
The  trunk  was  split  into  two  fragments,  one  seven¬ 
teen,  and  the  other  twenty-two  feet  long.  These 
fragments,  so  heavy  that  one  of  them  would  require 
the  combined  strength  of  four  men,  and  the  other 
that  of  eight  men,  to  lift  it,  were,  nevertheless,  pro¬ 
jected  by  the  lightning  to  the  distance  of  about 
seventeen  yards. 

In  January,  1762,  lightning  struck  the  church  of 
Breag,  in  Cornwall,  the  southwest  pinnacle  of  the 
tower  of  which  it  destroyed.  A  stone,  weighing  one 

5 


98 


MECHANICAL  EFFECTS  OF 


hundred  and  seventy  pounds,  was  projected  from  the 
roof  of  the  church  to  a  distance  of  sixty  yards  in  the 
direction  of  the  south.  Another  fragment  of  stone 
was  projected  to  the  north  to  a  distance  of  400  yards. 
A  third  was  projected  to  the  southwest. 

About  the  middle  of  the  last  century,  a  rock  of 
micaceous  schist,  measuring  105  feet  long,  10  feet 
wide,  and  about  4  feet  thick,  was  struck  by  lightning 
at  Funzie,  in  Scotland,  and  was  broken  into  three 
principal  fragments,  not  counting  smaller  pieces. 
One  of  these  fragments  twenty -six  feet  long,  ten  feet 
wide,  and  four  feet  thick,  had  been  merely  inverted 
in  its  position.  Another,  28  feet  long,  7  feet  wide, 
and  5  feet  thick,  was  projected  over  the  hill  to  a  dis¬ 
tance  of  fifty  yards.  The  remaining  piece,  forty  feet 
long,  was  projected  in  the  same  direction,  with  still 
greater  force,  and  fell  into  the  sea. 

On  the  6th  of  August,  1809,  at  Swinton^  about  five 
miles  from  Manchester^  lightning  struck  the  house  of 
Mr.  Chadwick,  at  2  p.  M.  A  sulphurous  vapor  im¬ 
mediately  filled  the  house.  The  external  wall  of  a 
building  erected  against  the  house  as  a  coal-shed,  was 
torn  from  its  foundations,  and  raised  in  a  mass.  It 
was  transported,  maintaining  its  vertical  position,  to 
some  distance  from  its  original  place ;  -one  of  its  ends 
Avas  transported  nine  and  the  other  four  feet.  This 
wall  thus  raised  and  transported,  was  composed  of 
seven  thousand  bricks,  which,  independent  of  the 
mortar  by  which  they  were  cemented  together, 
would  have  weighed  about  twenty-six  tons.  This 
Avail  Avas  eleven  feet  high  and  three  feet  thick,  and  . 


THE  ELECTRICAL  DISCHARGE. 


99 


its  foundation  was  about  a  foot  below  the  level  of  the 
ground.  Above  this  coal-shed  was  a  cistern,  which, 
at  the  time  of  the  phenomenon,  contained  a  quantity 
of  water,  and  the  shed  contained  about  a  ton  of  coals.* 

The  first  Presbyterian  church  in  the  City  of 
Syracuse,  New- York,  was  struck  by  lightning.  -The 
church  had  lightning  rods  attached,  but  these  were 
improperly  fastened  to  the  walls  by  sharp-pointed 
staples  in  full  connection  with  the  main  rod.  The 
lightning  struck  the  spire,  ran  down  part  way,  when 
the  charge  divided,  following  a  staple  fastening  into 
the  building,  as  far  as  the  pointed  staple  extended. 
This  staple  terminating  in  the  dry,  hard  masonry, 
which  must  have  been  nearly  a  non-conductor,  the 
charge  blasted  out  a  portion  of  the  steeple, — throw¬ 
ing  the  broken  fragments  several  hundred  feet, 
much  after  the  manner  of  a  too  shallow  blast  in  a 
rock.  And  thus  the  beautiful  structure  was  saved 
the  dire  destruction  which  must  have  happened  had 
the  church  been  built  of  wood,  a  partial  conductor 
when  wet,  and  fastened  with  iron  bolts,  &c.  These 
facts  were  related  to  the  writer  a  few  months  since 
by  several  intelligent  and  respectable  citizens  of  that 
city,  who  were  eye-witnesses  to  the  accident,  each  of 
whom  saved  pieces  that  were  thus  blasted  out  of  the 
steeple.  The  mechanical  force  here  manifested  was 
precisely  like  that  of  gunpowder. 

In  the  shock  of  lightning  which  fell  on  His 
Majesty’s  ship  Elephant^  of  seventy-four  guns,  at 


*  Dr.  Lardner’s  Lect.  on  Science  and  Art,  toI.  ii.  p.  69. 


100 


MECIIANrCAL  PREFECTS  OF 


Portsmouth,  in  November,  1790,  all  the  iron  hoops 
and  wooldings  on  the  mainmast  were  burst  open 
and  broken  in  pieces,  and  some  of  the  parts  scat¬ 
tered  to  great  distances.  Some  of  these  hoops  were 
half  an  inch  thick,  and  five  inches  wide  ;  the  mast, 
although  of  immense  size,  being  about  three  feet  in 
diameter,  and  upwards  of  110  feet  in  length,  was 
entirely  shook  and  shivered  throughout."^  Now,  in 
.these  cases  we  do  not  find  any  melting  of  the  iron 
work :  we  observe  only  the  effects  of  a  terrific  me¬ 
chanical  power. 

Another  remarkably  interesting  instance  of  this 
effect  was  observed  in  the  case  of  His  Majesty’s  ship 
Desiree^  already  alluded  to  (p.  55),  struck  by  light¬ 
ning  in  Port  Antonio,  in  Jamaica,  in  the  autumn  of 
1803.  Admiral  Boss,  who  then  commanded  the 
ship,  states,  that  one  part  of  the  main-topmast  was 
found  on  the  following  morning  sticking  in  the  mud 
on  one  side  of  the  harbor,  and  another  part  in  a 
timber-yard  on  the  opposite  side. 

In  the  application  of  lightning  conductors  to 
buildings,  therefore,  we  have  to  consider  the  effect 
likely  to  be  produced  on  them  by  the  mechanical 
action  of  the  shock,  by  which  they  may  be  disjointed, 
twisted,  or  rent  asunder  in  various  ways.  Thus,  the 
small  conductor  of  linked  brass  rod,  at  Charles 
Church,  Plymouth,  struck  by  lightning  in  December, 
1824,  was  literally  torn  in  pieces  and  disjointed, 
and  many  of  the  links  twisted  into  the  shape  of  the 


*  Naval  Chronicle, 


THE  ELECTRICAL  DISCHARGE. 


101 


letter  S.  A  part  of  the  small  wire  rope  applied  as 
a 'conductor  to  the  Hotel  des  Invalides  at  Paris  was 
broken  into  small  pieces  an  inch  or  more  in  length, 
and  scattered  in  all  directions  bj  the  lightning 
which  fell  on  that  building  in  June,  1839.  This 
conductor  consisted  of  about  twenty  iron  wires 
twisted  together  as  a  rope ;  the  lead  surrounding 
the  lantern  was  torn  up  and  scattered,  but  without 
any  signs  of  fusion.* 

The  intensity  of  electrical  accumulation  having 
been  found  to  decrease  in  an  inverse  ratio  of  the 
square  of  the  opposed  surfaces,  some  electricians 
were  led  to  imagine  that  extent  of  surface  was  the 
great  desideratum  in  the  application  of  a  lightning 
conductor.  This  decrease  of  intensity,  however, 
does  not  affect  the  conditions  of  conduction  as 
regards  the  heating  effect  of  the  discharge,  for, 
whether  the  quantity  of  electricity  be  accumulated 
on  a  large  extent  of  surface,  or  on  a  small  one,  the 

*  Com'ptes  Rendus,  June  17,  1839. 

A  question  of  no  small  public  interest  arises  here  relative  to  the 
insurance  of  buildings  against  lightning,  which  has  been  assumed  to 
be  a  species  of  fire,  and  that  hence  all  buildings  damaged  by  light¬ 
ning  are  damaged  as  if  by  fire ;  but  this  is  certainly  not  the  ease. 
A  building  may  be  struck  by  lightning,  and  may  certainly  be  set 
on  fire  by  it ;  but  in  the  great  variety  of  cases  which  occur,  the 
damage  is  purely  of  a  mechanical  kind :  thus,  in  the  case  of  the 
spire  of  St.  Martins,  already  described,  no  damage  could  be  said  to 
have  arisen  from  fire,  and  consequently  no  responsibility  could 
attach  to  those  who  assured  it  against  fire  only ;  the  damage  was 
purely  mechanical,  and  must  be  classified  with  the  kind  of 
damage  occurring  from  a  heavy  gale  of  wind,  or  any  other  me¬ 
chanical  force. 


102 


MECHANICAL  EFFECTS  OF 


heating  effect,  when  the  discharge  does  occur,  is 
always  the  same.  Whatever  may  be  the  distance 
at  which  the  neutralization  of  the  forces  begins,  they 
always  unite  with  precisely  the  same  degree  of 
power,  the  quantity  of  electricity  being  the  same. 

This  question,  so  frequently  discussed,  has  not 
been  fully  appreciated  in  all  its  details,  for  although 
quantity  of  metal  is  an  essential  condition  of  a  light¬ 
ning  rod,  yet  it  is  likewise  desirable  to  place  the 
metallic  particles  under  as  great  an  extent  of  surface 
as  may  be  consistent  with  strength  and  durability, 
in  order  to  keep  down  the  intensity  of  the  shock, 
and  diminish  the  mechanical  action.  We  may,  in 
fact,  for  the  moment,  consider  a  conductor,  while  in 
the  act  of  carrying  off  a  charge  of  lightning,  as  an 
electrified  body.  Its  electrical  intensity,  therefore, 
is  very  much  less  with  a  large  surface  than  with  a 
small  one :  hence,  by  extent  of  surface,  we  diminish 
the  activity  of  the  passing  charge,  and  tranquillize 
its  mechanical  effect  on  the  conductor.  Thus  we 
find,  in  a  variety  of  cases  of  damage  by  lightning, 
that  the  passing  charge,  in  striking  on  large  ex¬ 
panded  sheets  of  metal,  has  become  comparatively 
tranquil,  and  has  been  traced  no  further,  whilst  in 
striking  on  larger  masses  of  metal,  exposing  but  a 
small  surface,  it  has  assumed  an  intensely  active 
state.  The  flash  of  lightning  which  struck  His 
Majesty’s  ship  Badger^  lyiiig  iii  Medway,  in 
August,  1822,  vanished,  after  striking  upon  the 
copper  lining  of  the  galley,  although  just  before,  it 
had  penetrated  the  mast,  rent  the  copper,  and  melted 


THE  ELECTRICAL  DISCHARGE. 


103 


the  lead  over  the  heads  of  two  large  bolts  in  the 
deck  beams. 

Although  the  general  tendency  of  a  discharge  of 
lightning  is  always  through  the  conductor,  as  being 
the  line  of  least  resistance  (p.  69),  yet  there  may 
arise  cases  in  which  the  electrical  forces  may  be  so 
circumstanced  as  to  affect  other  lines  of  action  near 
it,  and  in  which  damage  may  ensue.  Thus,  in  the 
French  frigate  Calypso^  fitted  with  a  wire  conductor 
of  small  surface,  two  men  in  the  main  chains,  who 
were  standing  in  a  slightly  interrupted  conducting 
communication  between  the  wire  and  the  sea,  were 
struck  senseless.  A  similar  case  is  related  by  M. 
Arago,  as  having  occurred  in  the  French  frigate 
Junon.  In  fact,  wherever  from  any  cause  the  re¬ 
sistance  in  the  direction  of  the  conductor  is  con¬ 
siderable,  the  chances  of  damage  in  some  other 
direction  become  multiplied.  Thus,  a  case  occurred 
at  Bayonne,  in  which  the  length  of  the  conductor 
was  unnecessarily  increased, — that  is  to  say,  instead 
of  terminating  at  once  in  the  ground,  it  was  led  off 
at  the  foot  of  the  building  on  semi-insulating  stakes  of 
wood  for  some  distance ;  the  charge  here  divided  upon 
other  lines  near  the  conductor,  and  caused  damage.* 

Provided  the  quantity  of  metal  be  present,  the 
form  under  which  we  place  it  is  evidently  of  no  con¬ 
sequence  to  its  conducting  power,f  since  it  would  be 

*  Annuaire  pour  1838,  p.  597. 

f  The  reader  will  observe  that  the  writer  is  speaking  of  the  cajva- 
city  of  metal  to  conduct  a  given  amount  of  electricity,  without  regard 
to  power  to  disperse  or  weaken  the  charge  by  edges  and  points. 


104 


MECHANICAL  EFFECTS  OF 


absurd  to  suppose  that  a  mass  of  metal,  under  any 
form,  did  not  conduct  electricity  in  all  its  particles, — 
indeed,  we  know  that  it  does  so,  and  that  it  is  im¬ 
possible  to  fuse  by  electricity  a  'portion  only  of  a 
homogeneous  metallic  plate  of  uniform  thickness. 
Again,  if  the  heating  effect  of  a  given  quantity  of 
electricity  on  a  metallic  wire  be  measured,  and  then 
the  wire  be  rolled  out  into  a  flat  surface,  or  otherwise 
drawn  out  and  placed  under  the  form  of  two  or  more 
smaller  ones,  still  the  same  heat  will  be  evolved 
when  conducting  the  same  charge  ;  ^  there  is  conse¬ 
quently  no  disadvantage  in  giving  a  lightning  rod  as 
much  superficial  capacity  as  possible  as  regards  con¬ 
ducting  power,  whilst,  on  the  contrary,  the  dimin¬ 
ished  intensity  attendant  on  it  is  very  advantageous : 
this  effect  of  superficial  conductors  appears  to  depend 
on  the  removal  of  the  electrical  particles  further  out 
of  the  sphere  of  each  other’s  influence.  In  a  dense 
solid  rod  they  may  be  supposed  to  be  in  a  state  of 
compression,  in  each  other’s  way,  as  it  were, — 
whereas,  by  expanding  the  same  quantity  of  metal 
into  a  larger  surface,  we  immediately  free  them  from 
this  condition,  and  allow  them  greater  space.f 

In  order,  therefore,  to  resist  the  heating  effect,  we 
require  quantity  of  metal ;  to  restrain  the  electrical 
intensity,  and  to  diminish  the  mechanical  force,  we 
require  extent  of  surface.  The  distinction  is  nice, 
but  it  is  a  very  important  one. 

*  Trans.  Royal  Society  for  182V. 

f  See  Phil.  Trans,  for  1884  and  1836,  pp.  232  and  450,  for  some 
further  inquiries  on  this  point  by  the  author. 


THE  ELECTRICAL  DISCHARGE. 


105 


Two  questions  here  present  themselves  which  de¬ 
mand  attentive  consideration,  viz.,  what  quantity  of 
metal  is  requisite  to  perfect  security,  and  to  what  ex¬ 
tent  will  a  lightning  rod  afford  protection, — in  other 
words,  what  is  the  sphere  of  its  influence  ?  These 
problems,  although  apparently  difficult,  admit  of  a 
satisfactory  solution — a  solution,  it  is  true,  depending 
,  on  the  results  of  experience,  but  still  perfectly  con¬ 
clusive  ;  for  it  is  here  to  be  remembered,  that  we  seek 
protection  not  against  discharges  of  lightning  which 
have  no  existence  out  of  the  imagination,  but  against 
such  as  have  fallen  within  the  experience  of  man¬ 
kind — not  against  convulsions  of  nature,  in  which  it 
would  probably  be  of  little  consequence  whether  we 
had  lightning  rods  or  not,  but  against  probable 
and  tangible  results  of  the  operation  of  a  given  nat¬ 
ural  agency,  with  the  laws  of  which  we  are  ill  ac¬ 
quainted.  Now,  we  have  the  recorded  experience 
of  more  than  a  century  to  guide  us  in  this  inquiry ; 
and  first,  with  respect  to  the  actual  quantity  of  elec¬ 
tricity  which  may  be  contained  in  a  flash  of  light¬ 
ning,  and  the  quantity  of  metal  requisite  to  resist 
its  effects. 


What  quantity  of  Metal  is  requisite  for  a  Lightning 

Rod? 

Perhaps  one  of  the  most  terrific  discharges  of 
lightning  ever  experienced,  was  that  in  the  case  of 
the  New- York  packet,  struck  by  lightning  in  the 
5^ 


106 


QUANTITY  OF  METAL  REQUISITE 


Gulf  Stream,  in  April  1827,  already  noticed  (p.  54). 
In  this  case  the  discharge  fell  on  a  pointed  iron  rod 
four  feet  long,  and  half  an  inch  in  diameter ;  some 
few  inches  only  of  the  rod  near  its  point  were  melted ; 
the  linked  iron  chain  which  descended  from  this  rod 
to  the  water,  about  a  quarter  of  an  inch  in  diameter, 
was  knocked  in  pieces  by  the  expansive  force  of  the 
shock,  and  some  of  the  links  fused.  The  flash  of 
lightning  not  only  melted  some  of  the  links,  but 
“  caused  them  to  burn  like  a  taper.”  “  The  melted 
iron  fell  in  glowing  drops  upon  the  deck,  which  was 
instantly  set  on  fire  wherever  the  burning  matter 
fell.”  “  Such  was  the  violence  of  the  shock,  that  the 
ship  recoiled,  or,  in  sea  phrase,  lurched  so  strongly, 
as  to  throw  down  the  people  on  the  deck.”*  The 
results  of  a  great  natural  experiment  are  here  pre¬ 
sented  to  us,  and  we  see  that  an  iron  rod  of  half  an 
inch  in  diameter,  effectually  resisted  a  flash  which 
fused  and  destroyed  a  chain  of  about  one  half  of  its 
dimensions. 

The  flash  of  lightning  which  struck  Her  Majesty’s 
ship  Rodney^  in  December  1838,  was  so  powerful 
that  it  quite  dispersed  the  topgallant-mast  in  small 
chips,  covering  the  sea  with  splinters,  set  fire  to  the 
main-topsail,  tore  a  piece  ten  feet  long  out  of  the 
topmast,  burst  thirteen  hoops  on  the  mainmast,  each 
five  inches  wide  and  half  an  inch  thick,  and  traversed 
the  mast  with  destructive  effect  for  fifty-three  feet. 
Now  this  charge  passed  without  fusion  on  the  cop- 


*  Report  of  Coimnission  on  Shipivreck  by  Lightning. 


FOR  A  LIGHTNING  ROD.  107 

per  funnel,  sixteen  inches  long,  ten  inches  in  diame¬ 
ter,  and  less  than  a  quarter  of  an  inch  thick,  belong¬ 
ing  to  the  topgallant  rigging. 

In  September  1833,  two  successive  discharges  of 
lightning  fell  on  His  Majesty’s  ship  Myacinth^  in  the 
Indian  Ocean,  and  descended  by  the  fore  and  main¬ 
masts  to  the  sea.  The  topgallant  and  topmasts 
were  literally  shaken  into  a  bundle  of  laths,  so  that 
they  could  scarcely  be  supported  ;  the  topmasts  thus 
shivered  were  from  eleven  to  twelve  inches  in  di¬ 
ameter  and  about  forty  feet  in  length.  This  destruc¬ 
tive  shock  was  safely  conducted  away  from  the  ter¬ 
mination  of  the  topmasts  by  a  chain  sheet  fifty  feet 
'  long,  made  of  iron  rod  half  an  inch  in  diameter,  and 
finally  through  the  ship  by  a  copper  pipe,  three 
inches  in  diameter,  one-eleventh  of  an  inch  thick, 
and  ten  feet  long ;  *  before  reaching  these  bodies, 
which  were  direct  conductors  to  the  sea,  the  discharge 
ravaged  and  destroyed  the  masts  through  a  distance 
of  nearly  eighty  feet ;  the  chain  did  not  show  any 
marks  of  fusion. 

In  the  summer  of  the  year  1760,  a  heavy  dis¬ 
charge  fell  on  a  conductor  fixed  on  a  house  in  Phila¬ 
delphia.  This  conductor  consisted  of  an  iron  rod, 
half  an  inch  in  diameter ;  it  extended  nine  feet  above 
the  chimneys,  and  terminated  in  an  iron  stake  in  the 
ground.  The  part  above  the  chimneys  was  tipped 
with  brass  rod,  about  a  quarter  of  an  inch  in  diame¬ 
ter,  and  ten  inches  long.  Mr.  West,  the  owner  of 


*  Report  of  Comynission  on  Lightning  Rods,  p.  44. 


108 


QUANTITY  OF  METAL  REQUISITE 


the  house,  judging  from  the  crash  that  the  conductor 
had  been  struck,  had  it  examined.  About  three 
inches  of  the  brass  rod  were  observed  to  have  been 
fused,  and  some  of  the  fused  metal  had  sunk  down 
about  the  remaining  part  of  the  rod,  forming  a 
rough,  irregular  cap  about  it.  The  house  was  not 
damaged,  nor  were  any  further  effects  produced  on 
the  conductor.* 

On  the  26th  of  January,  1838,  a  flash  of  light¬ 
ning  fell  on  Her  Majesty’s  ship  Dublin^  of  fifty  guns, 
at  Eio  de  J aneiro.  It  was  carried  off*  by  a  conductor 
of  long  copper  links,  each  link  being  about  a  quarter 
of  an  inch  in  diameter,  and  ten.  inches  long.  The 
conductor  was  “regularly  melted”  in  several  parts; 
these  fell  on  the  deck ;  other  parts,  which  remained 
attached  to  the  line  supporting  the  chain  along  the 
rigging  of  the  ship,  appeared  as  if  they  had  been 
exposed  to  a  very  fierce  heat.  This  line  was  not 
hurt,  nor  was  any  damage  done  to  the  rigging,  f 

A  house  was  struck  by  lightning  at  Tenterden, 
on  the  17th  of  June,  1774.  The  discharge  was  con¬ 
ducted  by  an  iron  bar  three-quarters  of  an  inch 
square,  but  produced  no  effect  on  it.;]; 

In  June,  1772,  a  discharge  of  lightning  fell  on 
the  Vicarage-house  at  Steeple  Ashton,  in  Wiltshire. 
The  iron  bell-wires  in  both  the  parlors  and  in  the 


*  Phil.  TVaws.jVol.  liii.  part  1, 
f  Report  on  ShlpwrecTc  by  Lightning,  p.  94. 
X  Phil.  Trans,  for  I'Z'ZS. 


FOR  A  LIGHTNING  ROD. 


109 


hall  were  entirely  dispersed,  except  in  their  hoisted  or 
double  portions.^ 

In  June,  1828,  a  heavy  flash  of  lightning  fell  on 
the  spire  of  Kingsbridge  church,  in  Devonshire, 
and  was  received  on  an  iron  spindle,  seven  feet  long, 
and  one  inch  in  diameter,  without  producing  the 
least  effect  on  it,  or  damaging  the  stones  around  it : 
but  on  leaving  the  spindle,  however,  it  shattered  the 
tower,  and  did  considerable  damage. 

In  the  case  of  Charles  church  at  Plymouth  (p. 
100),  although  the  wire  was  knocked  in  pieces  at  the 
points  of  junction,  and  considerably  bent,  it  was  not 
materially  damaged  by  fusion. 

“In  reviewing,  in  this  way,  a  great  variety  of 
cases  in  which  buildings  and  ships  have  been  ex¬ 
posed  to  appalling  storms  of  lightning  in  various 
parts  of  the  world,  and  throughout  a  century  of 
years,  we  are  enabled  to  appreciate  the  power  of 
metallic  bodies  to  carry  off  lightning  with  safety. 
Now  we  do  not  find  in  any  of  these  cases  that  a  con¬ 
ducting  rod,  or  other  mass  of  metal,  equal  in  sub¬ 
stance  or  conducting  power  to  a  rod  of  copper  half 
an  inch  in  diameter  and  six  inches  long,  has  ever 
been  fairly  melted.  On  the  contrary,  heavy  dis¬ 
charges  have  traversed  rods  of  less  dimensions  with 
safety.” 

Besides,  the  conducting  power  of  lightning  rods 
has  been  much  increased  of  late  by  improvements  in 
their  construction.  1st.  In  multiplying  the  number 


*  Fhil.  Trans,  for  17  7  8. 


110 


EXTENT  OF  THE  PROTECTING  POWER 


of  their  points.  2d.  In  perfecting  their  continuity. 
8d.  In  the  substitution  of  square  rods  for  round 
ones.  The  reasons  of  these  facts  will  appear  here¬ 
after.  We  will  here  stop  only  to  add,  what  Mr. 
Harris,  F.  K.  S.,  in  his  work  on  thunderstorms, 
affirms,  viz.,  “  when  an  acutely  terminated  lightning 
rod  receives  a  charge  of  lightning,  a  very  considera¬ 
ble  portion  of  the  charge,  if  not  the  whole,  runs  off 
in  an  attenuated  stream.” 

How  far  does  the  Protecting  Power  of  a  Lightning  Rod 

extend  f 

It  is  not  easy  to  assign  the  limit  of  the  protecting 
power  of  a  conductor.  The  French  philosophers 
consider  it  will  afford  protection  over  a  circle  equal 
to  twice  its  radius  ;*  this,  although  possible  in  cer¬ 
tain  cases,  is  by  no  means  a  general  truth.  All  the 
experience  we  have  of  the  operation  of  conductors 
on  discharges  of  lightning,  tends  to  the  conclusion, 
that  they  have  no  influence  whatever  in  determining 
the  course  of  such  discharges,  further  than  arises  out 
of  the  circumstance  of  their  furnishing  an  easy  line 
of  conduction.  That  they  do  not  always  afford  pro¬ 
tection  over  any  considerable  distance,  is  clear  from 
the  following  cases  : — 

Her  Majesty’s  ship  Endymion^  commanded  by 
Captain  the  Honorable  F.  Crey,  was  struck  by  light¬ 
ning  at  Calcutta,  in  March,  1842.  This  frigate  had 


*  Annales  de  Chimie  et  de  Physique,  vol.  26. 


OF  A  LIGHTNING  ROD. 


Ill 


a  chain  conductor  on  the  mainmast,  applied  in  the 
usual  way,  not  very  dissimilar  to  that  recommended 
in  the  report  of  M.  Gay  Lussac  to  the  Koyal  Acade¬ 
my  of  Sciences  at  Paris.  The  electrical  explosion, 
instead  of  falling  on  the  conductor,  struck  the  fore¬ 
mast,  shivered  the  top-gallant  and  topmast,  and 
damaged  the  lower  mast.  Now,  in  this  case,  the 
mast  struck  was  not  above  fifty  feet  distant  from  the 
mainmast,  which  was  furnished  with  a  conductor, 
and  had  a  radius  of  one  hundred  and  fifty  feet.* 

Her  Majesty’s  ship  ^tna  was  struck  by  several 
heavy  electrical  discharges  at  Corfu,  in  January, 
1830.  These,  for  the  most  part,  passed  down  a 
chain  conductor  attached  to  the  mainmast.  One  of 
the  discharges,  however,  struck  the  ship  near  the 
bow,  and  exploded  about  twelve  feet  above  the  fore¬ 
castle,  close  to  the  foremast,  knocking  down  all  the 
people  on  deck,  and  doing  other  damage.f 

The  Board-house,  at  Purfleet,  was  struck  by 
lightning  on  the  12th  of  May,  1777jX  ^  point  up¬ 

wards  of  forty  feet  from  the  conductor  with  which 
the  house  was  furnished.  The  damage,  it  is  true, 
was  small ;  a  few  stones  fastened  by  iron  cramps  not 
connected  with  the  conductor  were  thrown  down. 
The  Board-house  was  a  lofty  building,  with  a  pointed 
roof,  well  leaded,  and  connected  by  lead  gutters  and 
pipes  with  the  earth,  and  with  wells  forty  feet  deep, 
for  the  purpose  of  conveying  water  forced  up  to  a 

*  Ship’s  log,  and  private  letter. 

f  Ship’s  log.  X  Trans, 


112 


EXTENT  OF  THE  PROTECTING  POWER 


cistern  in  the  roof.  It  was  therefore  only  thought 
necessary  to  add  an  iron  spike,  about  ten  feet  long, 
to  the  middle  of  the  highest  part  of  the  roof  About 
one  hundred  and  fifty  yards  from  this  building  were 
five  powder  magazines,  each  one  hundred  and  sixty 
feet  long  and  fifty-two  feet  wide,  having  spiked  con¬ 
ductors  at  each  end,  projecting  ten  feet  above  the 
roofs,  and  connected  with  wells  of  water.  It  is  quite 
apparent  here,  that  so  far  as  relates  to  the  influence 
of  a  conductor  over  a  given  area,  the  experiment  is 
conclusive,  and  the  result  shows  that  we  cannot  al¬ 
ways  calculate  on  the  radius  of  protection ;  thus  con¬ 
firming  the  deductions  already  arrived  at*  (p.  72). 

The  Poor-house  at  Heckingham  was  struck  by 
lightning  on  the  17th  of  June,  1781,  which  damaged 
one  of  the  extreme  corners  of  the  building,  situate 
seventy  feet  from  the  pointed  conductors  with  which 
the  house  was  furnished.  Little  or  no  damage,  how¬ 
ever,  was  sustained.  The  house  consisted  of  a  cen¬ 
tral  range  of  buildings  and  two  flanks ;  in  general 
form,  approaching  that  of  the  letter  H.  There  were 
eight  chimneys ;  each  had*  a  pointed  conductor. 
The  flash  appears  to  have  divided  in  this  case  before 
reaching  the  ground  (p.  35).  One  portion  struck  on 
one  of  the  conductors,  and  was  carried  off ;  a  second 
struck  the  extreme  point  of  the  building,  and  set  it 
on  fire;  a  third  fell  on  the  earth  immediately  in 
front  of  it.f 

The  house  at  Tenterden,  already  referred  to  (p. 


*  Phil.  Tram,  for  1773.  f  Phil.  Tram.,  vol.  Ixxii.,  p.  377. 


OF  A  LIGHTNING  ROD. 


113 


108),  had  two  stacks  of  chimneys  at  each  end.  To  one 
of  these  stacks  was  fixed  a  conductor  of  iron  rod,  pro¬ 
jecting  five  feet  above  the  chimney.  Now,  the  dis¬ 
charge  fell  on  one  of  the  chimneys  fifty  feet  distant, 
at  the  opposite  end  of  the  building ;  being  the  chim¬ 
ney  diagonally  opposite  to  that  on  which  the  con¬ 
ductor  was  placed,  and  on  passing  to  the  earth,  it 
did  considerable  damage.  The  whole  of  this  shock 
was  finally  concentrated  on  an  iron  bar  three-quar¬ 
ters  of  an  inch  square,  and  produced  no  effect  on  it, 
as  already  noticed  (p.  108).  The  house  was  about 
thirty  feet  wide.* 

These  cases  evidently  throw  doubt  on  any  theo¬ 
retical  calculation  as  to  the  limit  of  distance,  within 
which  a  pointed  lightning  conductor  will  afford  pro¬ 
tection,  and  confirm  in  a  remarkable  way  the  views 
we  have  taken  of  electrical  discharges  from  the  at¬ 
mosphere  (p.  69) 


*  Phil.  Trans.,  17 7 5. 


SECTION  III. 


RESULTS  OF  THE  APPLICATION  OF  LIGHTNING 
RODS  TO  BUILDINGS  AND  SHIPS, 

FROM  THE  PERIOD  OF  THEIR  FIRST  BEING  EMPLOYED  IN 
THE  YEAR  1760. 


Introductory  Remarks. — "Whether  Metallic  Conductors  have  effectu¬ 
ally  defended  Buildings,  &c.  against  Lightning  ? — Whether 
Lightning  Rods  attract  Lightning? — Whether  pointed  Conduc¬ 
tors  actually  prevent  explosions  of  Lightning  ? — The  Phenome¬ 
na  observed,  when  concentrated  discharge  strikes  upon  a  Con¬ 
ducting  Rod. — Harmless  character  of  the  luminous  appearances 
observed  on  Lightning  Rods. — Division  of  the  Charge. — Instan¬ 
ces  in  which  Buildings  having  pointed  Lightning  Rods  are  said 
to  have  been  damaged  by  Lightning. — Precautions  when  exposed 
to  the  action  of  Thunderstorms. — Construction  of  Lightning 
Rods  applied  to  Buildings. — Practical  Deductions. — Concluding 
Observations. 


SECTION  III. 


Introductory  Remarks. 

In  the  preceding  sections  we  have  considered  the 
physical  conditions  of  a  thunderstorm,  and  the  laws 
and  mode  of  operation  of  electrical  discharges. 
From  these  inquiries  we  have  deduced  certain  prac¬ 
tical  results  relative  to  the  employment  of  metallic 
substances  under  the  form  of  lightning  rods,  as  a 
means  of  protection  against  the  calamitous  effects  of 
lightning. 

W e  now  propose  to  examine  such  evidence  as 
we  possess  of  the  efficacy  of  lightning  rods,  whether 
they  have  met  all  the  conditions  required  for  perfect 
security  against  discharges  of  atmospheric  electricity, 
without  endangering  the  buildings  to  which  they 
are  applied,  and  finally  to  inquire  into  the  validity 
of  certain  popular  objections  to  their  general  employ¬ 
ment. 

It  may  be  perceived,  that  in  all  these  researches 
we  have  adhered  carefully  to  the  safe  and  beaten 
path  of  inductive  science :  in  no  case  has  any  ad- 


118 


EFFICIENCY  OF  LIGHTNING  RODS 


vance  unwarranted  by  facts  been  attempted.  The 
same  caution  will  be  observed  in  examining  the 
different  views  which  have  been  entertained  of  the 
efficacy  and  action  of  lightning  rods.  For,  as  it  has 
been  beautifully  remarked  by  Lord  Bacon,  the  great 
father  of  inductive  science,  “Man,  who  is  the  ser¬ 
vant  and  interpreter  of  nature,  can  act  and  under¬ 
stand  no  further,  than  he  has  either  in  operation  or 
in  contemplation  observed  of  the  method  and  order 
of  nature.” 


W^hether  Lightning  Rods  and  other  Metallic  Conductors 

have  effectually  guarded  Buildings^  &c.  against 

Damage  by  Lightning. 

The  cases  in  which  continuous  metallic  con¬ 
ductors  have  afforded  complete  protection  from 
lightning,  are  by  no  means  few  or  inconclusive. 
W e  shall  proceed  to  detail  some  of  the  most  remark¬ 
able  of  such  instances.  Between  the  years  1820 
and  1830  several  church  towers  in  Devonshire  were 
struck  by  lightning:  amongst  these  were  Shaugh 
church,  on  the  southern  border  of  Dartmoor;  Al- 
phington  church,  near  Exeter ;  Marlborough  and 
Kingsbridge  churches,  on  the  southern  coast ;  and 
Charles  church,  at  Plymouth :  of  these,  one  only 
was  protected  by  a  lightning  rod,  viz.,  the  church 
at  Plymouth.  Now  it  is  an  important  fact,  that 
although  the  conductor  was  broken  in  pieces  by  the 
shock,  as  already  stated  (p.  100),  this  was  the  only 


AND  OTHER  CONDUCTORS. 


119 


instance  in  which  the  church  and  tower  escaped 
damage. 

The  church  of  St.  Michael  at  Charlestown,  was 
very  frequently  struck  and  damaged  by  lightning 
previously  to  the  year  1760,  when  a  lightning  rod 
was  applied  to  it.  It  has  never  suffered  since.* 

The  Dutch  church  at  New- York  was  struck  by 
lightning  in  the  year  1750,  and  again  in  1763.  The 
electrical  discharge  in  each  case  passed  over  the 
metallic  connections  between  the  hammer  of  the 
bell  and  the  works  of  the  clock, — as  in  the  cases  of 
Brixton  and  St.  Martin’s  churches,  already  men¬ 
tioned  (p.  100) ;  in  both  instances  portions  of  these 
connecting  wires  were  melted,  and  the  building  was 
damaged. 

In  1765,  an  iron  rod  was  applied  from  the  stem 
of  the  weathercock  along  the  exterior  of  the  build¬ 
ing,  and  continued  to  the  ground.  During  this  year 
there  again  fell  on  it  a  heavy  stroke  of  lightning : 
the  building,  however,  was  not  in  the  least  degree 
damaged,  nor  was  any  effect  observable  on  the  wire 
connecting  the  bell  with  the  clock. f 

The  chapel  of  the  chMeau  of  the  Count  Orsini, 
in  the  province  of  Carinthia  in  Hungary,  being  on 
an  elevated  site,  received  such  frequent  damage 
from  lightning,  that  divine  service  was  no  longer 
celebrated  there.  In  the  year  1730  a  single  dis¬ 
charge  occurred,  whieh  at  once  laid  the  bell-tower 
in  ruins.  In  1778  the  building  was  again  nearly 

*  Phil.  Trans.,  vol.  Ixiv.  p.  133. 

+  Annuaire.  for  1838,  p.  604. 


120 


EFFICIENCY  OF  LIGHTNING  RODS 


demolished  by  a  similar  explosion,  and  was .  again 
rebuilt.  The  great  discovery  of  Franklin,  however, 
began  now  to  be  appreciated,  and  a  pointed  light¬ 
ning  rod  was  applied  to  the  tower.  During  the 
next  five  years,  it  was  only  once  assailed  by  light¬ 
ning,  and  then  no  damage  ensued ;  nor  does  the 
building  appear  to  have  suffered  since.* 

The  royal  chateau  at  Turin  was  frequently 
damaged  by  lightning  up  to  the  year  1772,  when 
Beccaria  applied  lightning  rods  to  its  principal  roofs. 
Since  that  time,  although  frequently  menaced  by 
thunderstorms,  it  has  remained  uninjured. f 

The  fine  tower  of  St.  Mark,  at  Yenice,  more  than 
three  hundred  and  forty  feet  high,  was  repeatedly 
damaged  by  lightning,  to  which  from  its  elevated 
position,  it  was  greatly  exposed.  This  tower  ter¬ 
minates  in  a  pyramid  eighty-seven  feet  high,  on 
which  stands  a  wooden  figure  of  an  angel  covered 
with  copper.  The  detached  pieces  of  iron  employed 
in  its  construction  produced  (as  at  St.  Bride’s  church 
in  London)  (p.  86)  very  destructive  effects.  It  was 
damaged  severely  in  1388,  at  which  time  it  was  a 
wooden  structure.  In  1417  it  was  set  on  fire  by 
lightning,  and  destroyed.  In  1489  it  was  again 
struck,  and  the  pyramid  reduced  to  ashes.  It  was 
now  rebuilt  with  stone.  In  the  years  1548,  1565, 
and  1653,  it  again  suffered  from  the  same  cause,  and 
in  1745  a  stroke  of  lightning  fell  on  it  with  such 

*  Rozier,  xxiv.  p.  323. 

f  Annuaire,  p.  605;  Marbuch,  Enkyk.  der  Exp.  Physik.  vol.  i. 
p.  314. 


AND  OTHER  METALLIC  CONDUCTORS. 


121 


tremendous  force,  that  the  whole  tower  was  nearly 
ruined:  it  was  rent  in  no  less  than  thirty-seven 
places.  The  cost  of  repairs  in  this  instance  amounted 
to  eight  thousand  ducats.  In  the  years  1761  and 
1762  it  was  again  severely  damaged.* 

We  have  here  sufficient  evidence  of  the  frequent 
effects  of  lightning  on  this  building,  whilst  unpro¬ 
tected  by  a  conductor.  Now,  in  the  year  1766,  a 
lightning  rod  was  applied  along  the  exterior  of  the 
tower,  reaching  from  the  metallic  figure  on  the  top 
of  the  pyramid  to  the  ground.  Since  this  period  we 
find  no  further  account  of  its  having  suffered  in  the 
least  degree  from  the  effects  of  lightning. 

We  have  already  noticed  the  application  of  a 
lightning  rod  to  the  beautiful  tower  of  the  cathedral 
at  Sienna  (p.  92),  which,  although  frequently  struck 
and  damaged  by  lightning  before  the  application  of 
the  rod,  has  not  since  experienced  any  ill  conse¬ 
quences,  although  struck  by  lightning  in  a  similar 
way. 

In  Rozier’s  Journal^  vol.  xxii.,  we  find  an  inter¬ 
esting  and  circumstantial  account  of  a  powder  maga¬ 
zine  at  Glogau  in  Silesia,  struck  by  lightning  in 
May,  1782,  and  defended  by  a  pointed  lightning 
rod.  “  The  flash  was  seen  to  leave  the  cloud  and 
strike  upon  the  rod;  it  appeared  to  envelope  the 
whole  building  in  electrical  fire.  The  sentinel  on 
guard  lost  his  senses  for  some  minutes,  but  no  dam- 

*  Extract  from  registers  of  the  city;  Arago,  Annuaire  pour 
1838. 


122  EFFICIENCY  OF  LIGHTNING  RODS 

age  ensued.”  The  conductor  terminated  in  a  well 
of  water. 

It  may  be  well  to  contrast  this  result  with  the 
results  in  other  cases,  in  which  discharges  of  light¬ 
ning  have  fallen  in  a  similar  way  on  magazines  of 
gunpowder,  not  provided  with  lightning  rods. 

In  March,  1782,  about  the  same  period,  a  dis¬ 
charge  of  lightning  fell  on  a  magazine  at  Fort 
Marlborough,  in  Sumatra,  not  having  a  lightning 
rod,  and  set  fire  to  four  hundred  barrels  of  gun¬ 
powder.* 

The  magazine  in  the  vaults  of  the  church  of  St. 
Nazaire  at  Brescia,  a  large  depot  of  gunpowder  be¬ 
longing  to  the  republic  of  Yenice,  shared  a  similar 
fate,  in  August,  1769.  The  electrical  discharge 
struck  the  tower,  and  descending  to  the  vaults,  ex¬ 
ploded  above  207,600  pounds  of  gunpowder. f  By 
this  dreadful  catastrophe  above  three  thousand  per¬ 
sons  perished,  and  nearly  one-sixth  of  the  beautiful 
city  of  Brescia  was  destroyed. 

A  similar  accident  occurred  to  a  magazine  at 
Malaga,  in  August,  1780,  and  at  Tangiers,  in  May, 
1785.  At  Luxembourg,  in  June,  1807,  a  magazine 
of  gunpowder,  built  in  former  times  by  the  Spaniards 
on  a  solid  rock,  was  struck  by  lightning  and  blown 
up  :  more  than  28,000  pounds,  or  about  twelve  tons 
of  gunpowder,  were  fired,  by  which  the  lower  part 
of  the  town  was  laid  in  ruins.:]; 


*  Maksden’s  History  of  Sumatra,  third  edition,  p.  19. 
f  Akago,  Annuaire,  1838,  p.  488.  %  Idem. 


AND  OTHER  METALLIC  CONDUCTORS. 


123 


In  September,  1808,  a  magazine  near  Yenice 
was  exploded  by  lightning,  and  in  November,  1829, 
another  at  Navarino.*  In  the  East  Indies  there 
have  been  very  lately  two  explosions  of  this  kind, 
viz,,  a  magazine  at  Dum  Dnm,  and  a  corning-house 
at  Mazagon  :  both  these  establishments  were  unpro¬ 
vided  with  lightning  rods. 

Now  it  is  to  be  observed,  on  the  contrary,  that 
although  such  rods  have  been  employed  for  the  de¬ 
fence  of  these  buildings  from  lightning  for  more  than 
seventy  years,  yet  in  no  instance  in  which  a  light¬ 
ning  rod  has  been  applied,  has  any  explosion  hap¬ 
pened. 

The  protecting  effect  of  a  lightning  conductor 
was  well  shown  at  Philadelphia,  United  States,  in 
July,  1770 :  a  severe  thunderstorm  overspread  the 
city,  and  produced  electrical  discharges  in  four 
places,  so  that  three  houses  and  a  merchant  ship  in 
the  river  were  struck  by -violent  detonations.  One 
of  the  houses  had  a.  pointed  lightning  rod,  and 
escaped  damage :  the  other  houses,  on  the  contrary, 
together  with  the  merchant  ship,  suffered  considera¬ 
bly.  On  examining  the  point  of  the  conductor  on 
which  the  lightning  fell,  it  was  found  to  have  been 
melted.f 

The  old  church  of  St.  Paul’s,  in  London,  not 
having  been  provided  with  a  lightning  rod,  was 
twice  struck  by  lightning  and  damaged.  The  pre- 

*  Report  bj  Admiral  Rosamel  to  the  Minister  of  Marine,  No¬ 
vember,  1829.  t  -Annuaire^  p.  609. 


124 


EFFICIENCY  OF  LIGHTNING  RODS 


sent  still  more  elevated  building  having  lightning 
conductors  of  great  magnitude,  has  never  suffered 
from  this  source  of  danger.  * 

In  addition  to  these  instances  of  the  operation 
of  pointed  metallic  rods,  in  defending  buildings 
against  damage  by  lightning,  it  may  be  observed, 
that  edifices  furnished  with  continuous  metallic 
masses,  either  with  a  view  to  utility  or  ornament, 
have  seldom  if  ever  suffered  from  atmospheric  elec¬ 
tricity. 

The  learned  orientalist,  Michaelis,  stales,  that  the 
temple  of  Jerusalem  had  not,  during  ten  centuries, 
^xperimiced  a  single  condensed  electrical  explosion. 
Now,  in  examining  the  accounts  given  of  this  build¬ 
ing,  it  appears  to  have  been  covered  inside  and  out 
with  burnished  plates  of  metal, — Josephus  says  gold. 
The  top  was  covered  with  a  thick  gilding,  and 
bristled  with  long  pointed  iron  or  steel  pikes.  The 
object  of  this  appears  to  have  been  to  prevent  birds 
from  settling  on  the  gilded  dome.  Under  the  court 
of  the  temple  were  cisterns,  which  received  the  rain 
from  the  roof  through  metallic  pipes.  A  more  com¬ 
plete  system  of  efficient  conductors  of  lightning 
could  not  have  been  devised.  The  conditions  we 
have  insisted  on  (p.  90),  viz.,  that  of  bringing  the 
building  as  nearly  as  possible  into  the  same  electrical 
position  that  it  would  be  in,  were  it  a  complete 
metallic  mass,  are  here  fully  satisfied,  and  we  ac¬ 
cordingly  find,  that  this  building  never  sustained 


*  Phil.  Trans. 


AND  OTHER  METALLIC  CONDUCTORS. 


125 


the  slightest  damage  from  lightning,  although  from 
its  elevated  position  it  was  exposed  to  the  frequent 
and  terrible  storms  of  Palestine.  It  is  more  than 
probable,  from  the  circumstance  of  the  roof  having 
been  covered  with  cedar,  both  within  and  without, 
that  a  heavy  stroke  of  lightning  falling  on  it,  would, 
but  for  the  metallic  coatings,  have  set  it  on  fire. 
When  we  consider  (as  observed  by  Arago),  how 
carefully  the  ancients  recorded  instances  of  damage 
done ‘to  their  buildings  by  lightning,  it  is  impossible 
to  explain  the  silence  of  historians  on  this  point,  ex¬ 
cept  by  admitting  that  the  Jewish  temple  had  never 
suffered  in  thunderstorms. 

A  parallel  instance  is  found  in  the  case  of  the 
cathedral  at  Geneva.  This  building,  the  most  promi¬ 
nent  and  elevated  in  the  whole  city,  has  for  more 
than  two  centuries  enjoyed  a  perfect  immunity  from 
the  effects  of  lightning,  whilst  the  bell-tower  of  St. 
Gervais,  situated  much  lower  than  the  cathedral,  has 
been  frequently  struck  and  damaged. 

In  the  year  1771,  Saussure  investigated  the  cause 
of  this,  and  on  examination  found,  that  the  great 
central  tower  of  the  bathedral,  built  of  wood,  and 
which  had  existed  above  three  hundred  years,  was 
completely  covered  from  its  summit  with  tinned  iron 
plate :  this  communicated  at  the  base  of  the  tower 
with  the  various  metallic  masses  about  the  roofs,  and 
lastly  by  metallic  pipes  with  the  ground,  thus  form¬ 
ing  an  extensive  and  complete  series  of  conduc¬ 
tors,  equivalent  to  the  transmission  of  the  most 
powerful  electrical  discharges. 


126. 


EFFICIENCY  OF  LIGHTNING  RODS 


The  Monument  near  London  Bridge,  which  by 
its  construction  has  an  uninterrupted  series  of  con¬ 
ductors  reaching  through  its  interior,  from  the  urn 
on  its  summit  to  the  earth,  is  another  instance.  This 
building  has  remained  safe  amidst  the  many  furious 
thunderstorms  which  have,  since  its  erection  in  1677, 
frequently  spread  over  the  metropolis,  and  damaged 
some  of  its  principal  edifices. 

It  may  be  observed  as  a  general  truth,  that  build¬ 
ings  in  any  way  cased  or  supplied  with  metallic  sub¬ 
stances  continued  to  the  ground,  invariably  escape 
damage  from  lightning  ;  and  that  where  such  metal¬ 
lic  coverings  or  connections  are  only  partially  applied, 
the  damage  commences  where  they  cease,  and  on  the 
contrary,  ceases  where  they  commence.  Thus  one 
of  the  large  granite  chimneys,  above  a  hundred  feet 
high,  at  the  Eoyal  Victualling  Yard,  near  Plymouth, 
was,  on  the  25th  of  May,  1841,  rent  by  lightning 
sixty  feet  down,  as  far  as  the  copper  roofing  of  the 
building  in  connection  with  it :  here  all  damage 
ceased,  the  copper  having  free  conducting  commu¬ 
nication  with  the  earth  by  the  metallic  pipes  for 
carrying  off  the  rain. 

The  effects  of  lightning  on  St.  Peter’s  church  in 
London,  in  the  summer  of  the  year  1774,  are  most 
remarkably  conclusive  on  this  point.  The  spire  of 
this  church  was  surmounted  by  a  large  key  of  gilded 
copper,  and  was  covered  with  lead  as  far  as  the  brick 
tower ;  accordingly  so  far  no  damage  ensued,  but 
between  this  and  the  leaded  roof  of  the  church  the 
tower  was  much  rent.  At  the  roof,  the  metallic  con- 


AND  OTHER  METALLIC  CONDUCTORS. 


127 


duction  again  commenced,  and  continued  to  the 
ground ;  and  here  again  the  damage  ceased.* 

Such  are  some  of  the  most  striking  facts  bearing 
on  the  protective  operation  of  lightning  rods  on 
buildings :  we  will  now  proceed  to  examine  their 
influence  on  shipping. 

In  the  year  1839  the  Lords  Commissioners  of  the 
Admiralty  appointed  a  naval  commission  to  inves¬ 
tigate  the  best  method  of  applying  lightning  con¬ 
ductors  to  Her  Majesty’s  ships.  After  a  very  elabo¬ 
rate  inquiry,  they  drew  up  a  report  on  this  important 
question,  extending  to  more  than  eighty  folio  pages, 
and  containing  a  valuable  mass  of  oral  and  docu¬ 
mentary  evidence,  received  from  naval  officers,  men 
of  science,  and  other  competent  persons.  This  re¬ 
port  was  laid  on  the  table  of  the  House  of  Commons, 
and  in  February  1840  was  ordered  to  be  printed. 
One  of  the  points  to  which  the  commission  directed 
its  attention  was  this  :  “  Whether  in  a  case  in  which 
ships  not  having  lightning  conductors  have  been 
struck  by  lightning,  it  appears  that .  other  ships  in 
'company  homing  lightning  conductors,  have  either 
not  been  struck,  or  have  escaped  injury.”  The  fol¬ 
lowing  are  some  of  the  cases  which  were  brought 
under  the  notice  of  the  Commissioners : — 

In  1815  His  Majesty’s  ship  Norgc^  was  severely 
damaged  by  lightning,  whilst  the  Warrior^  of  sev¬ 
enty-four  guns,  with  a  pointed  conductor,  lying  close 
to  the  Norge^  received  no  injury.  The  electrical  ac- 


*  PKil.  Trans.,  vol.  Ixiv.,  p.  133. 


128 


EFFICIENCY  OP  LIGHTNING  RODS, 


tion  in  this  case  illuminated  the  linked  portions  of 
the  conductor,  and  appeared  to  stream  down  into  the 
sea.  There  were  many  other  ships  in  the  harbor, 
but  none  received  any  damage  except  one,  aiid  this 
ship  luas  the  only  one  which  had  no  conductor. 

In  February,  1824,  His  Majesty’s  ship  Milford^ 
not  having  a  lightning  conductor,  was  struck  by 
lightning  in  the  Ilamoaze,  Devonport,  and  damaged, 
whilst  His  Majesty’s  ship  CaledoJiia^  of  one  hundred 
and  twenty  guns,  about  eighty  fathoms  distant,  hav¬ 
ing  pointed  conductors,  escaped. 

In  September,  1824,  His  Majesty’s  ships  Phaeton 
and  Adventure  were  lying  at  Gibraltar  Mole:  the 
Phaeton  had  not  conductors,  but  the  Adventure  had  : 
the  ships  were  within  a  cable’s  length  of  each  other. 
Under  these  circumstances  the  Phaeton  was  struck 
and  damaged  by  lightning ;  the  Adventure  escaped. 

In  January,  1830,  His  Majesty’s  ships  Madagas¬ 
car^  AEtna^  and  Mosquito^  were  about  to  come  to  an 
anchor  off  Corfu.  A  violent  thunderstorm  arose, 
which  struck  and  severely  damaged  the  Madagascar 
and'  Mosquito^  the  ships  without  conductors :  the 
jEtna.,  which  had  a  conductor  at  the  main,  although 
struck  by  lightning  repeatedly  on  this  mast,  escaped. 

In  1837,  the  Cochin  tank-vessel,  in  Trincomalee 
harbor,  had  her  foremast  shivered  by  lightning, 
whilst  Her  Majesty’s  ship  Winchester.,  about  two 
cables,  length  distant,  escaped.  The  Winchester  had 
a  conductor,  and  the  lightning  was  observed  to 
stream  down  it;  the  tank- vessel,  on  the  contrary, 
was  undefended. 


AND  OTHER  METALLIC  CONDUCTORS. 


129 


In  N’ovember,  1837,  the  Pelican^  of  sixteen  guns, 
without  a  conductor,  was  struck  by  lightning  on  the 
coast  of  Africa,  and  damaged;  the  Waterwitcli^  an¬ 
other  of  Her  Majesty’s  ships,  at  anchor  within  a  short 
distance,  escaped. 

In  March,  1838,  Her  Majesty’s  ship  Ceylon^  in  ’ 
Malta  harbor,  was  struck  by  lightning,  which  shiv¬ 
ered  the  foremast ;  she  had  no  conductor.  Her  Ma¬ 
jesty’s  ships  Talavera  and  Bellerophon^  both  fur¬ 
nished  with  lightning  conductors,  escaped,  as  did  the 
sheers  for  masting  ships,  which  were  similarly  armed. 
This  instance  is  the  more  remarkable,  from  the  fact 
that  the  Ceylon^  as  a  receiving  ship,  had  only  a  short 
pole  above  her  foremast,  whereas  the  other  ships, 
being  fully  rigged,  their  masts  extended  above  one 
hundred  and  fifty  feet  into  the  air. 

“  In  addition  to  these  instances,”  say  the  Com¬ 
missioners,  “,we  beg  to  call  their  Lordships’  atten¬ 
tion  to  the  case  of  the  New- York  packet,  laid  before 
the  Lord  High  Admiral  in  1827,  by  the  Navy  Board. 

It  appears  that  on  her  passage  to  Liverpool,  in  1827, 
this  ship  was  struck  by  lightning,  and  sustained  con¬ 
siderable  injury.  The  conductor  was  not  up  at  the 
time;  but  the  weather  continuing  stormy,  it  was 
got  out,  and  triced  up  to  the  mast-head.  The  ship 
was  a  second  time  struck  by  a  most  severe  stroke 
of  electricity,  which  fused  the  chain,  and  passed 
into  the  water  without  doing  further  damage.” 
(pp.  52,  105.) 

The  following  are  some  additional  cases  con¬ 
clusive  of  the  efficacy  of  lightning  rods  as  a  defence 


130 


EFFICIENCY  OF  LIGHTNING  RODS, 


against  lightning,  the  ships  having  been  fitted  with 
pointed  conductors  fixed  in  all  their  masts  : — 

His  Majesty’s  frigate  Dryad  was  struck  by  light¬ 
ning  in  a  tornado  on  the  coast  of  Africa,  in  1830. 
Commander  Turner  says,  “  that  the  discharge  fell  on 
both  the  fore  and  mainmasts  with  a  loud  whizzing 
sound ;  the  thunder  was  nearly  simultaneous  with  the 
lightning,  and  the  ship  appeared  enveloped  in  fiames.” 

His  Majesty’s  frigate  Druid^  at  Eio  Janeiro,  in 
1832,  encountered  awful  lightning,  which  was  “con¬ 
ducted  safely  down  the  conductors  on  the  fore  and 
mainmasts.”  * 

His  Majesty’s  ship  Asia^  in  the  Tagus,  in  1831,  was 
assailed  by  lightning  during  a  squall,  with  heavy 
rain ;  the  electrical  explosion  passed  off  safely  upon 
the  conductor  on  the  mainmast.f 

Her  Majesty’s  frigate  Talbot^  in  July,  1842,  was 
struck  by  lightning  soon  after  getting  under  weigh 
at  Sheerness.  The  lightning  was  observed  to  fall 
immediately  on  the  conductor  when  the  cloud  burst 
over  the  mainmast  head.:j: 

The  cases  of  the  Beagle  and  Actoeon^  referred  to 
in  our  second  section — each  receiving  heavy  electri¬ 
cal  charges  upon  their  conductors,  without  harm — 
■  furnish  very  complete  and  important  evidence  of  the 
beneficial  operation  of  pointed  conductors. 

Lieutenant  Sulivan,  who  had  witnessed  the  effects 
of  lightning  in  shattering  the  mast  of  His  Majesty’s 

*  Report  of  Commission,  p.  94. 

I  Witnessed  by  Mr.  Sadler,  the  master  of  the  ship. 

X  Reported  to  the  Lords  of  the  Admiralty. 


AND  OTHER  METALLIC  CONDUCTORS. 


131 


ship  Thetis^  happened  to  be  on  duty  at  the  time  the 
electrical  discharge  fell  on  the  Beagle;  he  states 
that,  “  when  the  clouds  by  which  the  ship  was 
enveloped  burst  on  the  mast,  the  mast  and  ship  ap¬ 
peared  to  be  wrapped  in  a  blaze  of  fire ;  the  vessel 
trembled  under  the  crash  of  the  thunder,  and  a 
vibratory  whizzing  sound  was  heard  along  the  con¬ 
ductors.” 

Lieutenant  Bonham,  and  Mr.  May,  the  carpenter, 
'who  were  both  on  deck  when  the  Actoeon  was  as¬ 
sailed  by  lightning,  describe  very  similar  effects. 
The  discharges  occurred  within  a  fearfully  short 
distance  of  the  ship,  and  the  flashes  were  so  vivid, 
that  the  observers  were  for  a  time  deprived  of 
sight.  When  the  ship  was  struck,  the  lightning 
was  observed  to  fall  immediately  on  the  conductor ; 
the  crash  of  the  thunder  was  intense  and  simultane¬ 
ous  with  the  lightning.  The  cutlasses  stowed  around 
the  mast  rattled  in  their  stand,  and  there  was  a  loud 
whizzing  sound  upon  the  conductor,  which  appeared 
enveloped  in  electrical  fire.”^ 

These  cases,  which  have  much  in  common,  are 
characterized  by  well-known  phenomena  of  electri¬ 
cal  action;  they  have  occurred  in  various  parts  of 
the  world,  at  different  times,  and  have  been  reported 
on  by  persons  in  no  way  interested  in  perverting  the 
facts  ;  hence,  no  doubt  can  remain  as  to  the  decisive 
evidence  they  afford,  of  the  protecting  power  of 
pointed  conductors. 


*  Account  by  the  master. 


132 


WHETHER  LIGHTNING  RODS 


Whether  Lightning  Rods  attract  Lightning. 

Amongst  the  objections  made  to  the  employment 
of  lightning  rods,  there  appears  to  have  been  none 
so  popular,  and  at  the  same  time  so  plausible,  as  this, 
viz.,  that  by  setting  up  pointed  conductors,  we  invite 
lightning  to  our  buildings,  which  otherwise  would 
not  fall  on  them ;  that  should  the  quantity  of  elec¬ 
tricity  discharged  be  greater  than  the  rod  can  carry 
off,  the  redundant  quantity  must  necessarily  act 
with  destructive  violence;  and  that  since  we  can 
never  know  the  quantity  of  electricity  which  may 
be  accumulated  in,  and  be  discharged  from,  the 
clouds,  it  is  not  improbable  but  that  any  conductor 
which  we  can  conveniently  apply,  may  be  too  small 
for  the  safe  conveyance  of  such  a  charge. 

Although  the  advocates  of  these  opinions  have 
never  adduced  any  substantial  fact,  or  any  known 
law  of  electricity,  in  support  of  them ;  although  they 
have  never,  by  any  appeal  to  experience,  shown  that 
buildings  armed  with  lightning  rods  have  been 
struck  by  lightning  more  frequently  than  buildings 
not  so  armed,  nor  demonstrated  any  single  instance 
in  which  an  efhcient  lightning  rod,  properly  ap¬ 
plied,  has  failed  to  afford  protection, — nevertheless 
such  views  have  been  commonly  entertained :  in¬ 
deed  so  strenuously  have  they  been  insisted  on, 
and  that,  too,  by  persons  of  education  and  influence, 
that  the  Grovernor-general  and  Council  of  the  Honor¬ 
able  the  East  India  Company  were  led  to  order  the 
lightning  rods  to  be  removed  from  their  powder- 


ATTRACT  LIGHTNING. 


133 


magazines  and  otlier  public  buildings,  having  in  the 
year  1838  come  to  the  conclusion,  from  certain 
representations  of  their  scientific  officers,  that  light¬ 
ning  rods  were  attended  by  more  danger  than  ad¬ 
vantage  ;  in  the  teeth  of  which  conclusion,  a  maga¬ 
zine  at  Dum  Dum,  and  a  corning-house  at  Mazagon, 
not  having  lightning  rods,  were  struck  by  lightning 
and  blown  up.* 

In  a  work  on  Canada,  published  so  lately  as  the 
year  1829,f  we  find  the  following  passage :  “  Science 
has  every  cause  to  dread  the  thunder  rods  of 
Franklin:  they  attract  destruction,  and  houses  are 
safer  v/ithout  than  with  them.  Were  they  able  to 
carry  off  the  fluid  they  have  the  means  of  attracting, 
then  there  could  be  no  danger,  but  this  they  are  by 
no  means  able  to  do.”  Assertions  such  as  these, 
appealing  as  they  do  to  the  fears  of  mankind,  rather 
than  to  their  dispassionate  and  sober  judgment,  have 
not  altogether  failed  in  obtaining  that  sort  of  tem¬ 
porary  favour  which  so  frequently  attends  a  popular 
prejudice,  promulgated  without  reason,  and  received 
without  proof.  Not  only  is  the  idea  that  a  lightning 
rod  invites  lightning  unsupported  by  any  fact,  but 
it  is  absolutely  at  variance  with  the  whole  course  of 
experience. 

The  notion  that  a  lightning  rod  is  a  ^positive 
eyil,  appears  to  have  arisen  entirely  out  of  assump- 

*  Correspondence  with  the  Honorable  Board  of  Directors ;  Pro¬ 
fessor  Daniell  and  Dr.  O’Shanghnessy. 

I  Three  Tears  hi  Ca7iada.  By  F.  McTaggart,  Civil  Engineer  in 
tlie  service  of  the  British  Government. 


134 


WHETHER  LIGHTNING  RODS 


tions,  and  a  partial  consideration  of  facts.  Thus  in 
consequence  of  the  track  of  a  discharge  of  lightning 
being  always  determined  through  a  certain  line  or 
lines,  which  upon  the  whole  least  resist  its  progress, 
it  has  often  been  found  to  fall  in  the  direction 
of  pointed  metallic  bodies,  such  as  vanes,  vane- 
spindles,  iron  bars,  knives,  &c.  The  instances  in 
which  these  bodies  seem  to  have  determined  the 
course  of  lightning  have  been  carefully  recorded, 
the  phenomena  being  peculiarly  striking  and  re¬ 
markable  (p.  86) ;  but  on  the  other  hand,  no  atten¬ 
tion  has  been  given  to  those  instances  in  which 
lightning  has  altogether  avoided  such  bodies,  and 
passed  in  other  directions,  (p.  72.)  Now  it  will 
be  found,  as  we  shall  presently  show,  that  the  action 
of  a  pointed  conductor  is  purely  passive.  It  is 
rather  the  patient  than  the  agent ;  and  such  con¬ 
ductors  can  no  more  be  said  to  attract  or  invite  a 
discharge  of  lightning,  than  a  watercourse  can  be 
said  to  attract  the  water  which  flows  through  it  at 
the  time  of  heavy  rain. 

We  have  shown  in  a  former  section  (p.  106),  what 
quantity  of  metal  is  really  sufficient  for  the  perfect 
conduction  of  any  quantity  of  lightning  liable  to  be 
discharged  in  the  most  severe  thunderstorms:  there¬ 
fore,  to  assume  that  any  conductor  which  may  be 
applied  is  not  sufficiently  capacious,  is  to  reason 
against  experience,  and  to  resort  to  a  species  of 
argument  quite  foreign  to  the  conditions  of  the  case. 
It  would  be,  as  if  we  were  to  insist  upon  the  danger  of 
applying  water  pipes  to  buildings,  under  the  assump- 


ATTRACT  LIGHTNING. 


135 


tion  that  we  do  not  really  know  what  quantity  of 
rain  may  possibly  fall  from  the  clouds,  and  that 
hence  the  pipe  may  after  all  be  too  small  to  con¬ 
vey  it. 

In  all  these  reasonings  we  should  recollect,  as 
already  explained  (p.  12),  that  the  forces  in  operation 
are  distributed  over  a  great  extent  of  surface,  and 
that  the  point  or  points  upon  which  lightning  strikes, 
is  dependent  on  some  peculiar  condition  of  the  in¬ 
tervening  air,  and  the  amount  of  force  in  operation, 
— not  on  the  mere  presence  of  a  metallic  body  pro¬ 
jecting  for  a  comparatively  short  distance  into  the 
atmosphere, — “  that  such  bodies  provoke  the  shaft 
of  heaven  is  the  suggestion  of  superstition,  rather 
than  of  science.”* 

We  shall  now  leave  the  theoretical  discussion  of 
this  question,  and  direct  attention  to  the  facts  them¬ 
selves,  and  examine  how  far  the  evidence  deducible 
from  such  facts  is  conclusive  upon  this  important 
point. 

During  the  thunderstorm  which  spread  over  the 
neighborhood  of  Plymouth,  in  May,  1841,  the  elec¬ 
trical  discharge  struck  one  of  the  high  chimneys  at 
the  Yictualling-Yard,  as  already  mentioned  (p.  126) ; 
it  fell  also  on  the  topmast  of  the  sheer-hulk  off  the 
Dock- Yard,  about  a  mile  and  a  half  distant.  Now 
the  circumstances  attendant  on  these  discharges  of 
lightning  bear  directly  on  the  question  before  us. 
The  chimney  at  the  Yictualling-Yard  is  a  round 

^  Leslie,  Edin.  Phil.  Magazine. 


136 


WHETHER  LIGHTNING  RODS 


column  of  granite,  about  one  hundred  and  twenty 
feet  high,  attached  to  the  bakehouse ;  it  has  not  a 
particle  of  metal  in  its  construction^  nor  has  it  any 
projecting  point  It  stands  at  a  distance  of  about  one 
hundred  yards  from  a  clock-tower  in  the  same  yard ; 
which,  on  the  contrary,  has  not  only  a  metal  vane, 
and  cross-pieces  of  metal,  indicating  the  four  cardinal 
points,  but  its  dome  is  covered  with  copper,  and 
there  is  a  large  conductor  continued  partly  within 
and  partly  without  the  tower,  from  the  dome  to  the 
ground.  In  the  sheer-hulk  a  very  small  metallic 
wire  was  led  along  the  pole  topmast,  and  connected 
with  the  large  metallic  chains  attached  to  the  mast 
and  sheers:  the  height  of  this  pole  was  compara¬ 
tively  low,  and  it  was  completely  overtopped  by 
the  neighbouring  spars  of  the  line-of-battle  ship 
Cornwallis^  ^igg^k,  and  fitted  with  conductors 

on  each  of  her  masts.  Now  when  the  disruptive 
discharges  took  place,  they  fell  on  the  granite 
tower,  which  had  not  a  single  metallic  substance  in 
its  construction,  and  on  the  low  flagstaff  pole  of 
the  sheer-hulk’s  mast,  notwithstanding  that  the  clock- 
tower  near  the  chimney  offered  every  possible  “in¬ 
vitation  to  the  discharge,  and  the  great  altitude  of 
the  line-of-battle  ship’s  spars  were  in  the  most  favor¬ 
able  position  for  “attracting”  the  electrical  explo¬ 
sion.  The  chimney  was  rent  for  sixty  feet ;  the 
flagstaff  of  the  hulk’s  mast  was  slightly  injured,  and 
the  small  wire  broken  and  fused ;  the  lower  mast 
and  chains  were  uninjured. 

On  the  25th  of  March,  1840,  Her  Majesty’s  ships 


ATTRACT  LIGHTNING. 


137 


Powerful  and  Asia^  each  of  eighty -four  guns,  were 
anchor  within  a  short  distance  of  each  other  in 
Yourla  Bay,  in  the  Mediterranean.  The  Asia  had 
the  fixed  pointed  conductors  attached  to  each  of  her 
masts;  the  Powerful  was  unprovided  with  any  light¬ 
ning  conductor  whatever.  Under  these  conditions 
they  were  both  exposed  to  a  severe  thunderstorm.  A 
discharge  of  lightning  fell  on  the  Powerful^  the  ship 
without  conductors,  and  shivered  some  of  her  spars ; 
whilst  the  Asia^  where  every  supposed  “  invitation  ” 
to  the  discharge  was  most  prominent,  experienced  no 
ill  effect. 

If  no  other  cases  were  on  record,  these  alone, 
would  be  sufficient  to  dispel  all  apprehensions  of  a 
metallic  conductor  “  attracting  or  inviting  ”  lightning. 
A  great  number  of  instances,  however,  equally  clear 
and  satisfactory,  exist ;  from  these  we  have  selected 
the  following : — 

Amongst  some  interesting  remarks  on  the  effects 
of  lightning,  by  Professor  Winthrop,  communicated 
by  Dr.  Franklin  to  Mr.  Henley,  it  is  stated,  that  a 
tree  which  stood  at  the  distance  of  fifty-two  feet  only 
from  a  pointed  conductor  attached  to  a  house,  was 
struck  by  lightning  and  shivered,  while  the  conduc¬ 
tor  and  house  escaped,* — that  is  to  say,  the  lightning 
fell  on  a  body,  v/hich,  according  to  the  prevalent 
notion,  had  little  or  no  attraction  for  it,  and  held  out 
no  “  invitation,”  in  preference  to  one  which  did, — a 
fact  totally  at  variance  with  the  whole  assumption. 


*  Phil.  Trans,  vol.  Ixiv.,  p.  152. 


138 


WHETHER  LIGHTNING  RODS 


We  have  already  adverted  to  the  case  of  the 
Southampton  (p.  72),  in  which  a  heavy  electrical  dis¬ 
charge  fell  upon  the  sea  close  to  the  ship,  during  a 
thunderstom  on  the  east  coast  of  Africa.  But  what 
makes  this  case  especially  applicable  to  the  question 
now  under  consideration,  is  the  circumstance,  that 
all  her  masts  were  fitted  with  fixed  lightning  con¬ 
ductors,  which  terminated  in  copper  spikes.  The 
storm  was  awful,  and  it  is  stated  by  Mr.  Martin,  the 
master,  to  have  lasted  from  ten  p.m.  to  two  A.M. 
“  The  night  was  pitchy  dark,  from  the  density  of  the 
surrounding  clouds:  the  roar  of  the  thunder  was  inces¬ 
sant,  and  the  flashes  of  lightning  frequently  so  vivid, 
as  to  affect  the  sight  for  some  minutes,”  yet  no  ill 
effect  was  experienced  ;  the  electrical  discharge  was 
not  drawn  down  in  an  explosive  form  exclusively 
upon  the  conductors,  although  it  actually  fell  with 
violence  upon  the  sea  close  to  the  vessel. 

Similar  effects  were  observed  in  His  Majesty’s 
ship  Sapphire^  armed  with  pointed  conductors  of  the 
same  kind.  Captain  Wellesley,  who  commanded 
this  ship,  states  that  “the  lightning  was  so  vivid,  and 
the  flashes  so  quick  in  succession  all  around  the  ship, 
that  although  the  duty  to  be  done  was  important,  I 
hesitated  to  expose  the  crew  to  them  yet  the  ship 
was  not  struck.”  In  another  place  he  states,  “that 
the  Sapphire  often  met  with  very  severe  lightning, 
but  it  was  never  attracted  to  her.”f 

The  frequent  instances  in  which  lightning  avoids 

^They  were  afraid  to  hoist  the  boats  out. 
f  Report  of  Commission  on  Shipwreck  hy  Lightning. 


ATTRACT  LIGHTNING. 


139 


the  most  prominent  parts  of  of  buildings,  and  falls 
obliquely  upon  some  point  far  removed  from  them, 
may  be  further  adduced  as  evidence  against  the  at¬ 
tractive  influence  of  such  projections.  The  long  zig¬ 
zag  track  of  lightning,  arising  from  the  resistance  of 
the  air  to  its  more  direct  path,  may  cause  it  to  fall 
very  obliquely  on  the  earth’s  surface,  as  is  well 
known:  indeed  some  of  the  directions  of  the  zig¬ 
zag,  may  become  almost  horizontal.  Now,  in  these 
cases,  the  pointed  extremities  of  a  tower,  or  the 
masts  of  ships,  have  no  influence  whatever  on  the 
course  of  the  explosion ;  which,  on  the  principles 
already  explained  (p.  70),  finds  its  way  through  the 
least  resisting  interval.  Mr.  Alexander  Small  states, 
in  a  letter  to  Dr.  Franklin,  that  he  saw  an  explosion 
of  lightning  pass  before  his  window  in  a  direction 
nearly  horizontal,  and  strike  a  clock-tower  far  be¬ 
neath  its  summit. 

In  the  discharge  of  lightning,  which  fell  on  His 
Majesty’s  ship  Opossum  in  the  English  Channel  in 
March,  1825,  “  a  peal  of  thunder  burst  on  the  main 
rigging,  and  split  the  topmast  cap.”*  Her  Majesty’s 
ship  Pique  was  struck  by  lightning  in  the  St.  Law¬ 
rence,  in  November,  1839,  by  a  discharge  which  fell 
on  the  foremast  just  beneath  the  head  of  it,  and 
from  thence  passing  down  the  mast,  did  considerable 
damage.  Such  cases,  although  comparatively  rare, 
and  to  a  certain  extent  exceptions  to  the  general 
course  of  lightning,  are  still  sufiicient  to  show  how 


*  Ship’s  log. 


140 


WHETHKR  LIGHTNING  RODS 


little  the  direction  of  electrical  explosions  is  deter¬ 
mined  by  the  influence  of  points  considered  as  mere 
attractors^  and  that  it  is  only  when  they  can  contrib¬ 
ute  to  the  equalization  of  the  opposite  electrical 
forces,  that  lightning  strikes  on  them.  Franklin,  in 
endeavoring  to  draw  off  the  electricity  of  a  charged 
sphere  by  means  of  a  pointed  wire,  found  that  the 
point  when  placed  on  a  rod  of  glass  or  wax,  had  no 
action  on  it.* 

When  this  large  mass  of  evidence  is  duly  con¬ 
sidered,  together  with  the  fact,  that  lightning  strikes 
indiscriminately,  trees,  rocks,  and  buildings,  and  even 
the  ground  near  them,  we  are  compelled  to  admit 
that  properly  constructed  lightning  rods  are  perfectly 
precise  in  their  operation,  and  that  the  common 
notion  that  they  “invite  destruction”  to  our  build¬ 
ings,  is  not  warranted  by  any  sound  argument  drawn 
from  experience. 

It  may  not  be  unimportant  to  notice  here  the 
following  extract  from  the  Memoirs  of  the  Count  de 
Forhin^  already  alluded  to.  (p.  21.)  In  describing  the 
large  St.  Helmo’s  fires,  observed  in  the  vane  of  the 
mainmast,  he  says,  “  I  ordered  one  of  the  sailors  to 
take  it  (the  vane)  down ;  but  scarcely  had  he  taken 
the  vane  from  its  place,  when  the  fire  fixed  itself  on 
the  head  of  the  mainmast,  from  which  it  was  impos¬ 
sible  to  remove  it  ;”f  so  that  the  presence  of  the 
metallic  point  was  not  at  all  necessary  to  the  elec¬ 
trical  discharge. 

*  Franklin’s  Letters,  p.  66. 

f  Ijctters  on  Electricity.  By  the  Abb4  Nollet. — Vide  Phil. 
Trans,  for  1753,  p.  201. 


ATTRACT  LIGHTNING. 


141 


Before  quitting  the  subject  of  the  absolute  pro¬ 
tection  from  lightning  afforded  by  conductors,  the 
Naval  Commission  inquire,  whether,  according  to 
the  common  prejudice,  conductors  have  the  power 
of  attracting  a  flash  of  lightning,  which  in  their 
absence  would  not  have  occurred  ;  and  their  report 
states  “  that  the  instances  of  accidents  to  ships 
without  conductors^  and  the  comparatively  rare  occur¬ 
rence  of  lightning  being  observed  to  strike  on  a 
conductor,  would  tend  to  negative  such  a  supposi¬ 
tion.”*  They  further  consider,  from  the  instances 
which  were  submitted  to  them,  of  ships  without 
conductors  having  been  struck  with  lightning,  in  the 
presence  of  ships  furnished  with  them,  which  were 
not  so  struck,  that  most  complete  evidence  is 
afforded  “  either  of  the  little  influence  exerted  by 
such  conductors  in  inducing  or  attracting  an  ex¬ 
plosive  discharge,  or  of  their  efficacy  in  harmlessly 
and  imperceptibly  conveying  away  electricity  to  the 
water.”f 


Whether  in  certain  cases  pointed  Conductors  actually 
prevent  Explosions  of  Lightning  from  falling  on 
Buildings.  The  Phenomena  observed  when  a  com 
centrated  Discharge  strikes  upon  a  Conductor. 

Coulomb  proved  by  actual  experiment,  that  the 
depth  of  the  electric  fluid  on  a  conductor,  always 
increases  in  a  rapid  proportion  in  approaching  the 


*  Report  of  Commission,  p.  4. 


f  IdeuQ. 


142 


DO  POINTED  CONDUCTORS  AVERT 


edges ;  and  that  the  effect  is  still  more  augmented  at 
corners,  which  may  be  regarded  as  two  edges  com¬ 
bined.  The  effect  is  still  further  increased  if  any 
part  of  a  conductor  have  the  form  of  a  point.  Now 
the  pressure  of  the  air  is  probably  the  only  force 
which  retains  the  electric  fluid  on  a  conductor ;  and 
it  is  evident  that  if  at  the  edges,  corners,  or  angular 
points  of  a  conductor,  the  electric  depth  be  so  much 
increased  that  the  force  of  the  electric  fluid  shall 
exceed  the  restraining  pressure  of  the  atmosphere, 
the  electricity  must  escape.  Accordingly,  it  is  found 
practically  impossible  to  accumulate  any  quantity  of 
electricity  on  a  conductor  furnished  with  points.* 

To  discharge  a  Leyden  phial  silently.  When  a 
large  jar  is  fully  charged,  which  would  give  a  vio¬ 
lent  shock,  put  one  of  your  hands  in  contact  with 
its  outside  coating,  and  with  the  other  hand  hold  a 
sharp-pointed  needle ;  and  keeping  the  point  di¬ 
rected  towards  the  knob  of  the  jar,  proceed  gradually 
towards  it,  until  the  point  of  the  needle  touches  the 
knob.  This  operation  discharges  the  jar  com¬ 
pletely,  and  the  operator  will  either  receive  no 
shock  at  all,  or  so  small  a  one  as  can  hardly  be 
perceived.  The  point  of  the  needle,  therefore,  has 
silently  and  gradually  drawn  all  the  charge  from  the 
inside  of  the  Leyden  phial. 

If  this  experiment  be  performed  in  the  dark, 
the  point  of  the  needle  will  appear  illuminated  in 
its  way  toward  the  knob  of  the  phial,  which  is 
another  proof  of  its  drawing  off  the  charge.f 

*  Noad's  Electricity,  p.  13.  f  Rees"  Encyc,  vol.  13. 


EXPLOSIONS  OF  LIGHTNING? 


143 


The  Electrified  Cotton.  Take  a  small  lock  of  cot¬ 
ton  (c),  extend  it  in  every  direction  as  muck  as  may 
be  practicable,  and  by  means  of  a  linen  thread  about 

Fig.  14 


N 

five  or  six  inches  long,  or  by  a  thread  drawn  out  of  the 
same  cotton,  tie  it  to  the  end  of  the  prime  con¬ 
ductor  P;  under  this,  attach  in  a  similar  way  an¬ 
other  lock  (6),  and  to  this  a  third  lock  (a) ;  and 
then  let  the  electrical  machine  be  put  in  action,  and 
the  locks  of  cotton  on  being  electrified,  will  imme¬ 
diately  swell  out,  by  repelling  their  filaments  from 
each  other,  and  will  stretch  themselves  towards  the 
nearest  conductor.  In  this  situation,  the  machine 
continuing  in  action,  present  the  end  of  a  finger  or 
the  knob  of  a  wire,  toward  the  lower  lock  of  cotton, 
and  this  will  then  immediately  move  towards  the 


144 


DO  POINTED  CONDUCTORS  AVERT 


finger,  or  the  point  N,  endeavoring  to  touch  it, 
much  in  the  same  way  that  the  petty  fragments  on 
the  lower  surface  of  a  thundercloud  lean  toward  the 
earth.  On  presenting  a  needle  at  N.  to  the  lowest 
lock,  a,  it  immediately  shrunk  back  upon  the  lock 
and  this  again  upon  c,  and  all  together  upon  the 
conductor  p,  where  the  locks  remained  as  long  as 
the  needle  continued  under  them.  Eemove  the 
needle,  and  the  cotton  will  come  again  toward  the 
finger.  Present  the  needle,  and  the  cotton  will 
shrink  again ;  which  clearly  shows  that  the  needle, 
being  sharp-pointed,  draws  off  the  electric  fluid  from 
from  the  cotton,  and  puts  it  in  a  state  of  being  at¬ 
tracted  by  the  prime  conductor ;  which  effort  can¬ 
not  be  produced  by  a  wire  having  a  blunted  end,  or 
a  round  ball  for  its  termination. 

Dr.  Franklin  observes,  “  that  electricity  is  not 
more  disposed  to  leave,  or  more  easily  drawn  off 
from  any  one  part  of  an  electrified  sphere  than  from 
another.  But  that  is  not  true  of  any  other  figure. 
From  a  cube  it  is  more  easily  drawn  at  the  corners 
than  at  the  plane  side,  and  so  from  the  angles  of  a 
body  of  any  other  form,  and  still  more  easily  from 
the  angle  that  is  the  most  acute.  For  the  reasons, 
why  electrified  bodies  discharge  their  electricity  upon 
unelectrified  bodies  more  easify,  and  at  a  greater  dis¬ 
tance  from  their  angles  and  points  than  from  their 
smooth  sides,  may  not  be  easily  -determined.  Differ¬ 
ent  philosophers  have  advanced  different  theories ; 
but  of  the  nature  of  points  all  are  agreed. 

“  Those  points  will  also  discharge  into  the  air. 


EXPLOSIONS  OF  LIGHTNING? 


145 


when  the  body  is  overcharged,  without  bringing  any 
non-electric  near  to  receive  what  is  thrown  off.  For 
the  air,  though  an  electric  per  se,  yet  has  always  more 
or  less  water  and  other  non-electric  matters  mixed 
with  it ;  and  these  attract  and  receivQ  what  is  so  dis¬ 
charged. 

“But  points  have  a  property,  by  which  they 
draw  on  as  well  as  throw  off  the  electric  fluid  at 
greater  distances  than  blunt  bodies  can.  That  is,  as 
the  pointed  part  of  an  electrified  body  will  discharge 
the  electricity  of  that  body,  or  communicate  it 
farthest  to  another  body,  so  the  point  of  an  unelectri¬ 
fied  body  will  draw  off  the  electrical  fluid  from  an 
electrified  body,  farther  than  a  blunter  part  of  the 
same  unelectrified  body  will  do.  Thus  a  pin  held 
by  the  head,  and  the  point  presented  to  an  electrified 
body,  will  draw  off  its  electricity  at  a  foot  distance  ; 
when,  if  the  head  were  presented  instead  of  the  point, 
no  such  effect  would  follow.  To  understand  this,  we 
may  consider,  that  if  a  person  standing  on  the  floor 
would  draw  off  the  electrical  fluid  from  an  electrified 
body,  an  iron  crow  and  a  blunt  knitting-needle  held 
alternately  in  his  hand,  and  presented  for  that  pur¬ 
pose,  do  not  draw  with  different  forces  in  proportion 
to  their  different  masses.  For  the  man,  and  what  he 
holds  in  his  hand,  be  it  large  or  small,  are  connected 
with  the  common  mass  of  unelectrified  matter ;  and 
the  force  with  which  he  draws  is  the  same  in  both 
cases,  it  consisting  in  the  different  proportion  of  elec¬ 
tricity  in  the  electrified  body  and  that  common  mass. 
But  the  force  with  which  the  electrified  body  retains 


146 


DO  POINTED  CONDUCTORS  AVERT 


its  electricity  by  attracting  it,  is  proportioned  to  the 
surface  over  which  the  particles  are  placed;  i.  e.  four 
square  inches  of  that  surface  retain  their  electricity 
with  four  times  the  force  that  one  square  inch  retains 
its  electricity.  And  as  in  plucking  the  hairs  from  the 
horse’s  tail,  a  degree  of  strength  not  sufficient  to  pull 
away  a  handful  at  once,  could  yet  easily  strip  hair 
by  hair ;  so  a  blunt  body  presented  cannot  draw  off 
a  number  of  particles  at  once ;  but  a  pointed  one, 
with  no  greater  force,  takes  them  away  easily,  parti¬ 
cle  by  particle. 

“  These  explanations  of  the  power  and  operation 
of  points,  when  they  first  occurred  to  me,  and  while 
they  first  floated  in  my  mind,  appeared  perfectly 
satisfactory  ;  but  now  I  have  wrote  them,  and  con¬ 
sidered  them  more  closely  in  black  and  white,  I  must 
own  I  have  some  doubts  about  them  ;  yet,  as  I  have 
at  present  nothing  better  to  offer  in  their  stead,  I  do 
not  cross  them  out:  for  even  a  bad  solution  read, 
and  its  faults  discovered,  has  often  given  rise  to  a 
good  one,  in  the  mind  of  an  ingenious  reader. 

“  Nor  is  it  of  much  importance  to  us  to  know  the 
manner  in  which  nature  executes  her  laws;  ’tis 
enough  if  we  know  the  laws  themselves.  ’Tis  of 
real  use  to  know  that  china  left  in  the  air  unsup¬ 
ported  will  fall  and  break  ;  but  how  it  comes  to  fall, 
and  why  it  breaks,  are  matters  of  speculation.  ’Tis 
a  pleasure  indeed  to  know  them,  but  we  can  preserve 
our  china  without  it. 

“  Thus  in  the  present  case,  to  know  this  power  of 
points  may  possibly  be  of  some  use  to  mankind. 


EXPLOSIONS  OF  LIGHTNING? 


147 


tltoTigli  we  should  never  be  able  to  explain  it.  The 
following  experiments,  as  well  as  those  in  my  first 
paper,  show  this  power.  I  have  a  large  prime  con¬ 
ductor,  made  of  several  thin  sheets  of  clothier’s  paste¬ 
board,  formed  into  a  tube,  near  ten  feet  long  and  a  foot 
diameter.  It  is  covered  with  Dutch  embossed  paper, 
almost  totally  gilt.  This  large  metallic  surface  sup¬ 
ports  a  much  greater  electrical  atmosphere  than  a 
rod  of  iron  of  fifty  times  the  weight  would  do.  It 
is  suspended  by  silk  lines,  and  when  charged,  will 
strike  at  near  two  inches  distance  a  pretty  hard 
stroke,  so  as  to  make  one’s  knuckle  ache.  Let  a  per¬ 
son  standing  on  the  floor  present  the  point  of  a 
needle  at  twelve  or  more  inches  distance  from  it,  and 
while  the  needle  is  so  presented,  the  conductor  can¬ 
not  be  charged,  the  point  drawing  off  the  fire  as 
fast  as  it  is  thrown  on  by  the  electrical  globe.  Let 
it  be  charged,  and  then  present  the  point  at  the  same 
distance  and  it  will  suddenly  be  discharged.  In  the 
dark  you  may  see  a  light  on  the  point  when  the  ex¬ 
periment  is  made.  And  if  the  person  holding  the 
point  stands  upon  wax,  he  will  be  electrified  by  re¬ 
ceiving  the  fire  at  that  distance.  Attempt  to  draw 
off  the  electricity  with  a  blunt  body,  as  a  bolt  of 
iron  round  at  the  end  and  smooth  (a  silversmith’s  iron 
punch,  inch  thick,  is  what  I  use),  and  you  must  bring 
it  within  the  distance  of  three  inches  before  you  can 
do  it,  and  then  it  is  done  with  a  stroke  and  crack. 
As  the  pasteboard  tube  hangs  loose  on  silk  lines, 
when  you  approach  it  with  the  punch  iron,  it  like¬ 
wise  will  move  towards  the  punch,  being  attracted 


148 


DO  POINTED  CONDUCTORS  AVERT 


while  it  is  charged;  but  if,  at  the  same  instant,  a 
point  be  presented  as  before,  it  retires  again,  for  the 
point  discharges  it.  Take  a  pair  of  large  brass  scales, 
of  two  or  more  feet  beam,  the  cords  of  the  scales  being 
silk.  Suspend  the  beam  by  a  packthread  from  the 
ceiling,  so  that  the  bottom  of  the  scales  may  be  about 
a  foot  from  the  floor.  The  scales  will  move  round 
in  a  circle  by  the  untwisting  of  the  packthread. 
Set  the  iron  punch  on  the  end  upon  the  floor,  in  such 
a  place  as  that  the  scales  may  pass  over  it  in  making 
their  circle.  Then  electrify  one  scale,  by  applying 
the  wire  of  a  charged  phial  to  it.  As  they  move 
round  you  see  the  scale  draw  nearer  to  the  floor,  and 
tip  more  when  it  comes  over  the  punch  ;  and  if  that 
be  placed  at  a  proper  distance,  the  scale  will  snap 
and  discharge  its  fire  into  it.  But  if  a  needle  be 
stuck  on  the  end  of  the  punch,  its  point  upwards, 
the  scale  instead  of  drawing  nigh  to  the  punch  and 
snapping,  discharges  its  fire  silently  through  the  point 
and  rises  higher  from  the  punch.  hTay,  even  if  the 
needle  be  placed  upon  the  floor  near  the  punch,  its 
point  upwards,  the  end  of  the  punch,  though  so 
much  higher  than  the  needle,  will  not  attract  the 
scale  and  receive  its  fire,  for  the  needle  will  get  it  and 
convey  it  away,  before  it  comes  nigh  enough  for  the 
punch  to  act.  And  this  is  constantly  observable  in 
these  experiments,  that  the  greater  quantity  of  elec¬ 
tricity  on  the  pasteboard  tube,  the  farther  it  strikes 
or  discharges  its  fire,  and  the  point  likewise  will  draw 
it  off  at  a  still  greater  distance.  The  same  experi¬ 
ment  slightly  varied,  is  given  by  Mr.  Harris :  cph^ 


EXPLOSIONS  OF  LIGHTNING? 


149 


Fig.  17,  is  a  long  bent  arm  of  light  brass  wire  bal¬ 
anced  bj  means  of  central  point  p  on  the  charging- 
rod  of  the  jar  J,  and  on  which  it  has  free  motion  in  all 
directions ;  A  is  a  light  disc  of  gilded  wood,  resem¬ 
bling  a  common  scale-pan,  covered  with  a  lock  of  fine 
cotton  wool,  and  suspended  by  conducting  threads 

Fig.  17. 


from  the  arm  ch  p.  A  pointed  body  B  is  placed  on 
the  same  conducting  base  t  t  with  the  jar.  If  the 
jar  be  now  charged,  the  cotton  in  the  scale-pan  will 
begin  to  extend  its  filaments,  and  the  whole  will  be 
attracted  toward  the  table,  much  in  the  same  way  as 
a  cloud  appears  to  be  attracted  toward  the  earth, 
causing  the  bent  arm  c  ph  Xo  assume  an  inclined 
position.  If  the  arm  be  now  caused  to  move  upon 
its  centre  y>,  so  as  to  allow  the  artificial  cloud  a  to 
approach  the  point  B,  the  arm  will  gradually  assume 
its  previous  horizontal  position,  in  consequence  of 


150 


DO  POINTED  CONDUCTORS  AVERT 


the  influence  of  the  point  in  neutralizing  the  oppo¬ 
site  forces.  As  the  artificial  cloud  continues  to  ap¬ 
proach  the  point,  this  action  proceeds  so  rapidly,  as 
frequently  to  produce  a  whizzing  sound,  the  bent 
arm  recovering  at  the  same  time  its  horizontal  posi¬ 
tion  ;  the  scale-pan  A,  so  far  from  being  attracted  by 
the  point,  actually  recedes  from  it,  and  very  faith¬ 
fully  represents  the  kind  of  operation  of  pointed 
bodies  on  charged  clouds,  viz.,  their  power  of  dis¬ 
charging  the  electricity  of  the  clouds  without  attract¬ 
ing  them. 

“  When  the  distances  and  charge  are  nicely  ad¬ 
justed,  this  experiment  is  very  striking  and  satis¬ 
factory. 

“  Now  if  the  fire  of  electricity  and  that  of  light¬ 
ning  be  the  same,  as  I  have  endeavored  to  show  at 
large,  in  a  former  paper,  this  pasteboard  tube  and 
these  scales  may  represent  electrified  clouds.  If  a 
tube  of  only  ten  feet  long  will  strike  and  discharge 
its  fire  on  the  punch  at  two  or  three  inches  distance, 
an  electrified  cloud  of  perhaps  10,000  acres  may 
strike  and  discharge  on  the  earth  at  a  proportionably 
greater  distance.  The  horizontal  motion  of  the  scales 
over  the  floor,  may  represent  the  motion  of  the  clouds 
over  the  earth ;  and  the  erect  iron  punch,  a  hill  or  high 
building  ;  and  then  we  have  electrified  clouds  passing 
over  hills  or  high  buildings  at  too  great  a  height  to 
strike,  which  may  be  attracted  lower  till  within  their 
striking  distance.  And  lastly,  if  a  needle  fixed  on  the 
punch  with  its  point  upright,  or  even  on  the  floor 
below  the  punch,  will  draw  the  fire  from  the  scale 


EXPLOSIONS  OF  LIGHTNING? 


151 


silently  at  a  mucli  greater  than  the  striking  distance, 
and  so  prevent  its  descending  towards  the  punch ;  or 
if  in  its  course  it  would  come  nigh  to  strike,  yet 
being  first  deprived  of  its  fire  it  cannot,  and  the 
punch  is  thereby  secured  from  the  stroke ;  I  say,  if 
these  things  are  so,  may  not  the  knowledge  of  this 
power  of  points  be  of  use  to  mankind,  in  preserving 
houses,  churches,  ships,  &c.,  from  the  stroke  of  light¬ 
ning?” 

Mr.  Wilcke,  who  made  some  very  acute  remarks 
on  Franklin’s  views  of  electricity,  states,  that  he 
witnessed  the  result  of  this  action  of  pointed  bodies 
on  the  great  scale  of  nature,  in  August,  1758.  A 
large  fringed  cloud,  strongly  electrified,  and  extend¬ 
ing  its  inferior  surface  towards  the  earth,  suddenly 
lost  its  electrical  character,  in  passing  over  a  forest 
of  tall  fir  trees.  The  ragged  and  depending  portions 
shrank  back  upon  the  main  cloud,  and  rose  up,  as  it 
were,  from  the  earth.* 

The  great  number  of  cases  we  have  cited  (pp.  118, 
182),  with  a  view  of  showing,  not  only  the  protecting 
effect  of  lightning  rods,  but  their  passive  character 
as  attractors  of  lightning,  may  be  further  adduced, 
in  illustration  of  this  peculiar  property  of  pointed 
conductors.  Indeed,  it  is  almost  impossible  to  ac¬ 
count  for  the  fact  of  so  many  buildings  being  repeat¬ 
edly  struck  by  lightning,  before  they  were  furnished 
with  lightning  rods,  and  so  seldom  struck  afterwards, 
and  that  lightning  has  seldom,  if  ever,  been  observed 


*  Franklin’s  Letters,  p.  851. 


152 


PHENOMENA  OBSERVED  WHEN 


to  fall  in  an  explosive  form  upon  buildings  involving 
pointed  metallic  conductors  in  their  construction, — 
without  admitting  that  the  conductors  had  rapidly 
neutralized  the  electrical  state  of  the  air,  and  so  pre¬ 
vented  the  occurrence  of  a  dense  explosion. 

We  find  this  effect  especially  apparent  (p.  118) 
in  the  case  of  the  tower  of  St.  Mark  at  Venice,  the 
chapel  of  the  Count  Orsini,  the  temple  of  Jerusalem, 
the  monument  of  London,  the  cathedral  at  Geneva, 
and  many  others ;  and  if  we  add  to  these  the  re¬ 
markable  instances  of  certain  ships  of  the  British 
navy,  enveloped  as  it  were  in  violent  thunder¬ 
storms  in  tropical  climates,  without  any  dense  ex¬ 
plosion  falling  on  them,  the  evidence  of  this  action 
of  pointed  conductors,  in  mitigating  the  fury  of 
electrical  discharges,  is  as  complete  as  any  evidence 
from  experience  can  be  imagined. 

We  have  deemed  it  worth  while  to  thus  extend 
illustrations  of  the  power  of  points  to  draw  on,  and 
to  throw  off  the  electrical  fluid,  on  account  of  the 
intrinsic  practical  importance  of  the  subject  to  the 
community,  who  have  churches  and  other  public 
buildings  to  protect,  and  to  private  citizens,  who 
have  lives,  houses,  and  various  kinds  of  property  ex¬ 
posed.  For,  without  a  due  appreciation  of  this  power 
of  points,  no  intelligent  conviction  can  be  had  as 
to  the  proper  construction  of  lightning  conductors. 

Phenomena  observed  when  a  dense  Explosion  of 
Electr  icity  falls  on  a  Lightning  Rod. 

Instances  in  which  the  forces  have  not  been  so 
rapidly  neutralized  by  the  action  of  pointed  bodies, 


EXPLOSIONS  FALL  ON  A  LIGHTNING  ROD.  153 

as  to  prevent  some  portion  of  tire  discharge  from 
falling  upon  the  conductor  in  a  concentrated  form, 
are  by  no  means  common :  when  they  do  occur, 
however,  the  explosive  action  subsides  in  striking 
on  the  point.  The  phenomena  in  such  cases  corres¬ 
pond  accurately  with  those  of  artificial  electricity, 
and  are  of  a  highly  interesting  character.  The 
crash  of  the  thunder  is  attended  by  a  loud  whizzing 
sound,  described  by  some  observers  as  the  rushing 
of  water,  or  like  the  sound  heard  on  lifting  the  valve 
of  a  steam  boiler;  at  the  same  time  the  conductor 
becomes  covered  with  a  luminous  glow  or  streak  of 
light,  and  appears  at  the  part  struck  to  be  enveloped 
in  electrical  fire. 

The  luminous  appearance  was  observed  at  an 
early  period  of  the  application  of  lightning  rods. 
When  the  heavy  discharge  fell  upon  the  tower  at 
Sienna,  in  1777,  several  persons  noticed  upon  the 
conductor  a  long  and  regular  train  of  light.*  At 
the  time  of  the  dense  electrical  explosions  which  fell 
upon  Her  Majesty’s  ships  Druid^  Beagle^  Dryad^ 
&c.  (p.  130),  the  observers  all  agree  in  representing 
the  discharge  as  attended  by  a  loud  whizzing 
sound,  and  upon  the  conductors  a  transient  glow 
of  light. 

These  phenomena  are  easily  produced  by  arti¬ 
ficial  means.  If  we  attempt  to  discharge  a  highly 
charged  jar  through  a  pointed  rod,  a  loud  whizzing 
noise,  in  the  direction  of  the  point,  will  be  heard. 


7^ 


*  Tilloch’s  Mag.,  viii.,  p.  318. 


154  HARMLESS  CHARACTER  OF  THE  LUMINOUS 

immediately  before  the  dense  explosion  takes  place. 
The  production  of  the  light  is  not  so  easily  accounted 
for;  but  the  results  of  scientific  inquiry  favor  the 
opinion  that  it  is  a  sort  of  glow,  between  metal  and 
air  immediately  in  the  points  of  contact ;  that  it  is 
of  a  perfectly  harmless  nature,  and  may  be  classed 
with  the  phosphorescent  flashes  attendant  on  the 
aurora  borealis,  or  with  the  streaming  of  ordinary 
electricity  in  the  exhausted  receiver  of  an  air-pump. 
It  may  be  produced  artificially  on  a  conducting 
wire,  either  by  increasing  the  electrical  charge,  in 
respect  of  the  size  of  the  wire,  or  diminishing  the 
atmospheric  pressure. 


Harmless  Character  of  the  Luminous  Appearances 
observed  on  Lightning  Rods. 

It  is  essential  to  distinguish  between  this  glow 
on  the  surface  of  lightning  rods  and  the  hea,t  evolved 
by  the  passing  shock.  We  have  already  shown  (p. 
109)  that  no  mass  of  metal,  equal  in  conducting 
power  to  a  copper  rod  half  an  inch  in  diameter  and 
two  feet  in  length,  has  ever  been  fused  or  even 
sensibly  heated  by  lightning;*  and  it  is  well  known 
that  any  quantity  of  electricity  may  be  discharged 
through  a  conducting  rod,  even  whilst  in  contact 
with  the  most  inflammable  compounds,  such  as  gun¬ 
powder,  &c.,  without  igniting  them,  provided  the 
temperature  of  the  rod  be  not  considerably  in- 


*  Shipvjrech  hy  Lightning,  Report  and  Evidence,  p.  13. 


APPEARANCES  OBSERVED  ON  LIGHTNING  RODS.  155 


creased  by  tbe  discharge.  If  the  atmospheric  pres¬ 
sure  about  such  a  wire  be  diminished,  we  immedi¬ 
ately  observe  it  covered,  at  the  instant  of  the 
discharge,  with  a  luminous  glow,  yet  it  is  not  sensi¬ 
bly  heated,  nor  will  inflammable  matter  in  contact 
with  it  be  inflamed. 

There  are  many  interesting  examples  on  record, 
of  the  small  degree  of  heat  of  this  species  of  electrical 
action.  The  St.  lielmo’s  fires,  and  other  electrical 
lights  which  so  often  settle  on  the  masts  and  ropes 
of  ships,  are  unattended  by  any  calorific  effect ;  and 
persons  during  electrical  storms,  have  appeared  to  be 
enveloped  in  weak  flames,  without  being  at  the  time  ^ 
in  any  way  conscious  of  it. 

A  remarkable  instance  of  the  harmless  nature 
of  these  appearances  was  observed  by  Eoss  and 
Sabine,  in  returning  from  their  last  Arctic  expe¬ 
dition.  In  the  Grreenland  seas,  during  a  dark,  cloudy 
night,  they  observed  a  sort  of  glow  discharge  on  the 
surface  of  the  water,  directly  in  the  ship’s  course. 
It  appeared  to  occupy  a  space  of  four  or  five  hun¬ 
dred  yards,  and  had  very  considerable  elevation. 
The  vessel  at  length  sailed  out  of  a  pitchy  darkness, 
directly  into  this  luminous  mass ;  all  at  once  the 
masts,  yards,  and  sails,  as  the  successive  masts 
passed  forward,  became  covered  with  light.  The 
ship  having  sailed  completely  through  it,  became 
again  involved  in  profound  obscurity.* 

*  Communication  from  Dr.  Robison  to  Mous.  Arago. — Annuoire 
for  1838,  p.  372. 


156 


DIVISION  OF  THE  CHARGE. 


This  was  evidently  one  of  those  glow  discharges 
already  explained  (p.  38).  The  deep  black  clouds 
covering  the  sky  being  particularly  indicative  of 
that  peculiar  condition  of  the  atmosphere  observed 
in  thunderstorms  (p.  52) ;  as  evidence  of  the  small 
heating  effect  of  this  species  of  electrical  light,  the 
result  is  very  important  and  conclusive. 


Division  of  the  Charge. 

Although  there  is  no  instance  on  record  of  an 
isolated  lateral  explosion  of  electricity  from  a  light¬ 
ning  rod,  yet  we  find  instances  in  which  the  dis¬ 
charge  has  divided  between  the  conductor,  and  other 
metallic  bodies  in  connection  with  the  earth. 

Arago,  in  his  valuable  “  Notices  sur  le  Ton- 
nerref  published  in  the  Annuaire  of  1838,  has 
quoted  an  instructive  case  of  this  nature."^  It  ap¬ 
pears  that  for  the  protection  of  a  house  in  the  United 
States  of  America,  a  lightning  conductor  had  been 
applied  on  the  outside  of  the  building,  similar  to 
that  represented  in  the  annexed  figure  (16),  in  which 
p  is  a  pointed  bar  of  iron  projecting  from  the  roof, 
N,  a  similar  bar  driven  into  the  ground,  at  p  ^  a 
small  brass  wire  connecting  the  bar.  At  the  point 
??,  inside  the  house,  stood  a  fowling-piece,  with  its 
barrel  against  the  wall,  and  separated  from  the  con¬ 
ductor  p  N  only  by  the  thickness  of  the  masonry. 
The  consequence  was,  that  when  a  discharge  of 


*  Franklin’s  Works,  vol  i,,  p.  361. 


DIVISION  OF  THE  CHARGE. 


157 


lightning  fell  on  the  conductor  at  p,  and  passed  on 
the  small  wire  P  %  it  divided  at  the  point  w,  upon 
the  two  circuits,  and  in  doing  this  broke  out  a  large 


Pig.  16. 


hole  in  the  wall  of  the  house,  and  shattered  the 
stock  of  the  gun  in  forcing  a  passage  to  the  earth. 
The  small  wire  p  t  was  completely  melted  so  far  as 
the  pointy??,  but  not  beyond  it ;  the  resistance  in  the 
direction  p  ^  K,  at  the  point  of  fusion  of  the  wire, 
evidently  exceeded  or  was  equal  to  the  resistance  in 
the  direction  p  isr ;  hence  the  metal  in  the  fowling- 
piece  evidently  saved  the  remaining  portion  of  the 
wire  n  t. 

The  cases  quoted  of  the  damage  by  lightning  to 
the  Hotel  des  Invalides,  at  Paris  (p.  101),  to  the 
French  frigate  La  Junon^  as  also  the  shock  expe¬ 
rienced  by  the  two  sailors  in  the  French  frigate 
La  Calypso^  are  all  instances  of  this  division  of 


168 


BUILDINGS  HAVING  CONDUCTORS 


the  charge  between  the  conductor  and  other  lines  of 
transit  to  the  earth  or  sea.  It  is  quite  clear,  that  in 
these  cases  the  resistance  to  the  progress  of  the  dis¬ 
charge  through  the  small  and  very  long  ropes  of 
wire,  exceeded,  or  was  at  least  equal  to,  the  resist¬ 
ance  in  other  directions ;  consequently,  these  in¬ 
stances  are  very  similar  to  the  preceding. 

‘‘  I  am  not  aware,”  says  Faraday,  in  speaking  of 
such  cases,  “  of  any  phenomenon  called  lateral  dis¬ 
charge,  which  is  not  a  diversion  of  the  primary 
current “  all  liability  to  a  division  of  the  main 
charge  would  decrease  in  proportion  to  the  capacity 
of  the  primary  conductor.”* 


Instances  in  which  Buildings  provided  with  pointed 
Conductors  are  said  to  have  heen  damaged  hy 
Lightning. 

Although  several  instances  have  occurred  in 
which  buildings  having  pointed  lightning  rods  have 
been  damaged  by  lightning,  yet  it  is  a  singular  fact, 
that  they  may  all  be  quoted  in  illustration  of  the 
great  advantage  of  such  rods,  in  safely  transmitting 
heavy  electrical  discharges  from  the  atmosphere. 

We  have  shown,  by  reference  to  a  variety  of 
cases,  both  the  small  influence  of  pointed  con¬ 
ductors  in  attracting  or  causing  explosions  of  light¬ 
ning,  and  the  liability  of  the  discharge  to  break  up, 
before  reaching  the  earth,  into  two  or  more  streams 


*  Report  and  Evidence  on  Shipwrech  hy  Lightning,  pp.  34,  35, 


DAMAGED  BY  LIGHTNING. 


159 


(pp.  135,  136).  In  tlie  cases  of  damage  by  lightning 
said  to  have  occurred,  notwithstanding  the  presence 
of  a  pointed  conductor,  the  electrical  discharge  has  di¬ 
vided  in  the  air  into  two  or  more  streams,  previously 
to  striking  the  building.  One  portion  has  commonly 
struck  upon  the  conductor,  and  been  carried  off  by 
it,  whilst  other  portions  have  fallen  on  points  far 
distant  from  the  conductor. 

The  first  instance  claiming  attention,  is  the  case 
of  the  church  of  “  Notre  Dame  de  la  Garde,”  at 
Genoa,  struck  and  damaged  by  lightning  on  the 
14th  August,  1779,  a  lightning  rod  having  been  ap¬ 
plied  to  it  in  the  previous  year. 

The  church  stands  on  one  of  the  highest  hills  in 
the  neighborhood  of  Genoa,  and  clouds  are  con¬ 
stantly  hanging  over  it ;  the  bell  .tower  to  which 
the  conductor  had  been  applied,  was  originally  even 
with  the  facade,  but  in  consequence  of  a  subsequent 
enlargement  of  the  church,  and  the  erection  of  a 
porch,  it  was  thrown  far  back.  The  lightning  con¬ 
ductor  commenced  from  a  stout  iron  rod,  tipped 
with  a  gilded  copper  point;  this  rod  projected 
from  the  top  of  the  bell-tower  three  feet  into  the 
air,  and  from  its  termination  a  stout  iron  bar  was 
continued,  and  led  out  through  a  window  over  the 
roof  of  the  church,  and  so  on  to  the  ground.  Before 
the  lightning  struck  the  church,  it  bifurcated  (p. 
36);  one  of  the  explosions  fell  on  the  conductor,  split 
open  the  gilded  copper  point,  and  was  conducted 
safely  to  the  earth :  the  other  explosion  struck  the 
porch  at  a  distance  from  the  conductor,  descended 


160  BUILDINGS  HAVING  CONDUCTORS 

into  the  church,  and  did  some  damage ;  several  per¬ 
sons  who  were  in  a  room  over  the  porch  felt  a  vio¬ 
lent  shock,  many  were  thrown  down,  but  not  hurt. 

This  account  has  been  obtained  from  the  Samm- 
lungen  zur  PJiysih^  for  1782  :*  the  writer  states  that 
the  accident  was  attributed  to  the  conductor,  but  he 
shows  that  if  the  conductor  had  not  been  there, 
much  greater  damage  must  have  ensued,  and  thinks 
it  is  perfectly  clear  that  the  church  was  struck  in  two 
places, — first  on  the  conductor ;  secondly,  upon  the 
unprotected  porch.  This  case,  therefore,  does  not 
furnish  any  argument  against  the  employment  of 
lightning  rods,  but  rather  shows  their  value,  and 
points  out  the  necessity  of  securing  the  portions  of  a 
building  which  are  distant  from  the  rod. 

The  case  already  alluded  to  (p.  Ill)  of  the  Board- 
house  at  the  Purfleet  magazines  having  been  struck 
by  lightning,  in  May,  1777,  is  another  instance  in 
which  a  building  furnished  with  a  lightning  rod  was 
damaged.  From  the  description  of  this  building,  it 
will  be  seen  that  the  corner  struck  was  forty-six  feet 
distant  from  the  point  of  the  conductor.  Little  or  no 
damage  was  done  :  a  few  stones  only  were  displaced. 
Now,  there  can  be  very  little  doubt  but  that  the 
conductor  really  carried  off  safely  and  silently  a 
great  portion  of  the  discharge  ;  it  is  impossible  to  ex¬ 
plain  on  any  other  principle  how  so  small  an  amount 
of  damage  ensued  from  so  heavy  a  discharge  as  this 
appears  to  have  been,  especially  if  we  suppose  it  to 


*  Vol.  ii,,  p.  588. 


DAMAGED  BY  LIGHTNING. 


161 


have  been  concentrated  upon  two  clamps  on  a  cor¬ 
ner  of  the  building.  The  probability  is,  that  the 
discharge  bifurcated,  as  in  the  preceding  case ;  and 
whilst  one  division  rushed  through  the  conductor, 
the  other  struck  a  distant  point  of  the  house.  The 
clamps  on  which  it  fell,  were  fixed  in  the  coping- 
stones  of  the  parapet,  and  were  about  seven  inches 
above  the  lead  gutters  of  the  roof,  which  constituted 
a  portion  of  the  general  system  of  conduction  to  the 
ground. 

The  discharge,  in  forcing  its  way  through  seven 
inches  of  bad  conducting  matter  to  the  lead  beneath, 
did  some  damage  by  an  intermediate  explosion,  but 
it  was  very  inconsiderable  ;  had  the  iron  clamps  been 
continued  to  the  general  mass  of  metal  on  the  roof, 
it  is  quite  certain  that  no  damage  whatever  would 
have  occurred. 

In  the  account  given  of  this  case  in  the  Transac¬ 
tions  of  the  Royal  Society^  it  appears  that  an  observer 
who  witnessed  the  descent  of  the  lightning,  saw  it 
divide  in  some  point,  p  (fig.  17),  into  “  three  fire-balls,” 
as  he  termed  them.  One  of  these  struck  in  the  direc¬ 
tion  of  the  conductor  at  c,  another  damaged  the  corner 
of  the  building  at  m,  together  with  a  shed  at  5,  and 
the  third  struck  upon  the  ground  in  front  of  the 
house,  near  a  gate,  at  G.* 

This  was  evidently  an  instance  of  the  trifurcation 
of  lightning  (p.  36),  one  of  the  divergent  branches 
or  streams  having  fallen  on  the  conductor.  But  this 


*  Phil.  Trayis.,  vol.  Ixxii.,  p.  377. 


162 


BUILDINGS  HAVING  CONDUCTORS 


part  of  the  explosion  was  discharged  safely  into  the 
earth,  whilst  the  shed  5,  and  corner  m,  which  were 
unprotected,  suffered.  This  case,  therefore,-  affords 


Fig.  17. 


conclusive  evidence  of  the  value  of  lightning  rods. 
The  committee  of  the  Eoyal  Society,  in  a  report  on 
this  circumstance,  considered  that  the  rods  were  not 
so  “  perfectly  applied  as  they  ought  to  have  been 
they  were,  however,  sufficiently  well  applied  to  meet 
any  discharge  of  lightning  likely  to  have  fallen  on 
them.  No  part  of  the  building  near  them  was 
damaged,  and  it  is  not  to  be  expected  that  they 
should  defend  parts  at  a  great  distance,  especially 
when  such  parts  are  the  first  exposed  to  an  elec¬ 
trical  cloud  moving  toward  them,  and  likely  to  strike 
upon  them  obliquely  (p.  135). 

The  instance  in  which  lightning  fell  upon  a  maga- 


DAMAGED  BY  LIGHTNING. 


163 


zine  of  powder  at  Bayonne,  in  February,  1829,  fur¬ 
nishes  another  remarkable  illustration  of  the  liability 
of  the  electrical  discharge  to  divide  in  the  air,  and 
strike  on  a  part  of  a  building  distant  from  a  light¬ 
ning  rod,  as  well  as  on  the  rod  itself.  This  case, 
which  was  reported  on  by  the  physical  section  of  the 
Eoyal  Academy  of  Sciences  at  Paris,  gave  rise  to 
much  interesting  discussion. 

The  building  is  about  fifty-six  feet  in  length,  and 
about  thirty -six  feet  wide :  it  is  covered  by  thick 
vaulted  masonry,  and  a  sloping  roof  with  gable  ends : 
these  were  protected  by  plates  of  lead ;  the  gutters 
also  were  of  lead,  and  there  were  the  usual  appen¬ 
dages  for  discharging  the  rain. 

The  lightning  rod  projected  about  twenty  feet 
above  the  building :  it  was  attached  to  the  lead  of 
the  roof  by  a  metallic  socket,  through  which  it 
passed,  and  which  was  soldered  to  one  of  the  lead 
coverings.  Instead  of  being  carried,  however,  di¬ 
rectly  into  the  earth  at  the  foot  of  the  wall,  it  was 
turned  outward,  at  about  two  feet  from  the  ground, 
and,  being  bent  at  right  angles,  was  continued  on 
semi-insulating  posts  of  wood  into  a  trench  filled 
with  charcoal,  distant  thirty- three  feet  from  the  wall. 

On  the  23d  of  February,  1827,  about  4  a.m.,  . a 
discharge  of  lightning  fell  on  this  building.  The 
•  point  of  the  conductor  was  melted,  and  the  plates  of 
lead,  by  which  it  was  attached  to  the  wood  posts  at 
the  foot  of  the  wall,  were  more  or  less  torn  and  per¬ 
forated  by  holes.  No  damage,  however,  ensued  to 
the  building  in  the  course  of  the  conductor.  At  the 


164 


BUILDINGS  HAVING  CONDUCTORS 


southwest  C9rner,  a  sheet  of  lead  covering  the  gable 
end  was  torn  out  immediately  over  a  point  where 
two  stones  of  the  cornice  were  united  by  an  iron 
cramp.  Hence,  as  in  the  case  of  the  magazine  at 
Purfleet,  this  distant  part  of  the  building  was  also 
visited  by  an  electrical  explosion. 

The  reporters  state,  that  the  conductor,  in  conse¬ 
quence  of  being  continued  at  so  great  a  distance  from 
the  building,  did  not  offer  a  sufficiently  easy  line  of 
transit  for  the  discharge  to  the  earth,  which  is,  they 
think,  evident,  from  the  damage  to  the  wooden  posts 
on  which  the  conductor  was  supported  :  hence  they 
infer,  that  the  discharge  divided  between  the  con¬ 
ductor  on  which  it  first  struck,  and  the  metals  of  the 
roof,  and  that  the  small  rent  on  the  lead,  on  the  south¬ 
west  angle,  was  the  result  of  this  division,  in  a  point 
through  which  the  electrical  discharge  found  its  way ; 
that  this  is  the  more  probable  from  the  circumstance 
of  the  rain  having  at  this  point  beaten  against  the 
walls,  and  so  increased  the  facility  of  conduction  by 
means  of  a  “  sheet  of  water,  to  the  ground.”* 

The  following  well  authenticated  instances  of 
recent  occurrence,  in  which  lightning  has  fallen  upon 
bodies  in  the  vicinity  of  conductors,  as  well  as  upon 
the  conductor  itself,  are  very  similar  to  those  just 
•described,  and  they  furnish  satisfactory  evidence  of 
the  nature  of  such  cases. 

Her  Majesty’s  brig  Racer ^  commanded  by  Cap¬ 
tain  J.  Hope,  was  struck  by  lightning  in  May,  1835, 


*  Annales  de  Chimie^  tome  xl.,  p.  391. 


DAMAGED  BY  LIGHTNING. 


165 


in  latitude  89°  north,  longitude  63°  west ;  a  chain 
conductor  was  up  at  the  mainmast.  The  electrical 
discharge  fell  with  destructive  violence  on  the  fore¬ 
topgallant  mast,  distant  from  the  conductor  about 
forty  feet,  at  the  same  time  sparks  were  seen  on  the 
chain,  and  a  rustling  noise  was  heard  throughout  its 
length*  (p.  131).  We  have  here  a  remarkable  illus¬ 
tration  of  the  nature  of  the  accident  at  Purfleet. 
The  conductor  evidently  transmitted  without  explo¬ 
sion  a  great  portion  of  the  discharge,  and  conse¬ 
quently  prevented  the  damage  which  must  have  en¬ 
sued,  had  the  whole  been  concentrated  on  a  single 
unprotected  point. 

Dr.  O’Shaughnessy  relates  the  following  instance 
of  the  bifurcation  of  lightning, f  which,  on  examina¬ 
tion,  will  be  found  to  have  a  very  forcible  application 
to  the  case  of  the  damage  done  to  the  magazine  at 
Bayonne.  It  appears  that,  in  May,  1837,  an  electri¬ 
cal  explosion  divided  upon  two  adjoining  houses  in 
Chowringhee,  East  Indies;  one  of  the  houses  not 
having  a  lightning  rod,  in  the  occupation  of  Dr. 
Goodeve,  was  struck  and  damaged,  whilst  the  ad¬ 
joining  house,  tenanted  by  Mr.  Trower,  and  to  which 
a  lightning  rod  had  been  applied,  escaped,  although 
a  portion  of  the  explosion  fell  on  it  with  great  vio¬ 
lence.  “Dr.  Goodeve,  while  walking  in  the  veran¬ 
dah,  saw  the  lightning  strike  Mr.  Trower’s  conductor, 
and  at  the  same  time  strike  his  own  house.”  The 

*  Ship’s  log,  with  remarks  by  Captain  J.  Hope,  R.  N. 

I  Reports  to  the  Honorable  the  Court  of  Directors  of  the  East 
India  Company. 


166 


BUILDINGS  HAVING  CONDUCTORS 


distance  of  the  damaged  part  of  Dr.  Groodeve’s  house 
from  the  conductor,  appears,  from  a  subsequent  ex¬ 
amination,  to  have  been  sixtj-six  feet,  about  the 
same  distance  as  that  in  the  case  of  the  Heckingham 
poor-house,  just  described. 

This  case  so  remarkably  conclusive  as  to  the 
protectiug  effect  of  lightning  rods,  has  nevertheless 
been  adduced  as  an  evidence  of  their  liability  to 
draw  down  greater  discharges  upon  buildings  than 
they  can  transmit,  thus  causing  damage  to  surround¬ 
ing  bodies ;  we  have,  however,  already  shown  (p.  136), 
that  pointed  metallic  rods  have  no  such  attractive 
influence,  and  that  discharges  of  lightning  are  de¬ 
termined  towards  the  earth  by  very  different  causes. 
But  even  if  it  were  true,  that  a  pointed  metallic  rod 
did  invite  or  attract  lightning  towards  it,  still  we 
cannot  suppose  it  to  attract  more  than  it  can  conduct, 
since  the  attraction  would  entirely  depend  on  the 
superior  conducting  power  of  metals ;  to  assert,  there¬ 
fore,  that  a  conductor  can  draw  towards  it  more  light¬ 
ning  than  it  can  conduct,  is  to  assert  in  other  words 
that  it  attracts  more  than  it  can  attract,  which  is  evi¬ 
dently  an  absurd  proposition. 

The  last  instance  which  Mr.  Snow  notices  of 
damage  done  by  lightning  to  a  building  furnished 
with  a  conductor,  is  the  case  of  the  Melville  Monu¬ 
ment,  in  St.  Andrew’s  Square,  Edinburgh.  It  con¬ 
sisted  of  a  pointed  metallic  rod,  which  passed  through 
the  statue,  and  was  connected  with  an  iron  chain 
led  through  a  hollow  way  in  the  staircase  to  the 
ground. 


DAMAGED  BY  LIGHTNING. 


167 


On  the  14th  of  July,  1837,  an  electrical  explo¬ 
sion  fell  on  this  building,  by  which  the  wooden  door 
leading  from  the  staircase  to  the  platform  of  the 
gallery  was  forced  off  its  hinges,  and  the  stones  at 
the  top  near  the  door  were  loosened.  On  examining 
the  conductor  after  the  accident,  it  appeared  that  the 
chain  connecting  the  pointed  rod  with  the  ground 
had  been,  by  accident  or  design,  drawn  up  for  some 
considerable  distance  through  the  hollow  way  in 
the  staircase,  and  coiled  round  a  stick  placed  across 
the  top  of  the  stone  tube  round  which  the  stair  was 
built.  The  stick  was  so  placed  as  to  press  against 
the  door  leading  to  the  platform,  in  order  to  keep  it 
shut. 

The  damage  in  this  case,  therefore,  did  not  arise 
from  any  failure  in  the  principle  on  which  the  con¬ 
ductor  was  applied,  but  entirely  in  consequence  of 
the  displacement  of  its  inferior  portion,  which  re¬ 
duced  it  to  the  condition  of  a  semi-insulated  mass  of 
metal. 

A  church  in  Connecticut,  in  which  were  assem¬ 
bled  the  congregation,  was  struck  by  lightning. 
Prof.  Brocklesby,  of  Trinity  College,  Hartford,  who 
related  to  the  writer  the  circumstances,  was  in  the 
house  at  the  time  of  the  explosion.  The  spire  had 
a  single  round  rod,  running  down  to  the  ground. 
The  charge  was  oblique,  and  came  in  a  direction  oppo¬ 
site  to  the  spire,  and  struck  the  end  of  the  church 
most  remote  from  the  steeple.  But  this  instance 
cannot  be  adduced  as  evidence  against  the  principle 
on  which  lightning  conductors  are  applied,  since, 


168 


BUILDINGS  HAVING  CONDUCTORS 


according  to  tire  known  laws  of  electricity,  the  rod 
could  render  no  protection  whatever — the  lightning 
not  coming  within  its  sphere  of  attraction. 

The  writer  would  add  the  case  of  Mr.  Platt’s 
house,  in  Deep  Eiver,  Connecticut,  already  alluded 
to,  under  the  head,  “  Ascending  or  Upward  Stroke.” 
This  instance  has  often  been  adduced,  as  an  argu¬ 
ment  against  the  efficiency  of  lightning  conductors. 
But  nothing  could  be  more  unfair.  I  know  not  who 
erected  the  two  rods  upon  this  house.  A.  M.  Quin- 
by,  Esq.,  of  this  city,  speaking  of  this  instance 
through  the  public  prints,  asserts,  “  that  they  were 
Spratt’s  patent,  put  up  by  a  Dr.  Minor,  of  Hartford, 
Connecticut;  but  they  were  so  improperly  con¬ 
structed  and  attached,  that  they  could  not  be  at  all 
responsible  for  the  harm  suffered  by  the  building.” 
The  disruptive  charge  being  upward,  and  occurring 
on  the  front  side  of  the  house,  and  the  rod  running 
down  only  on  the  back  side,  the  lightning  had  no 
chance  of  getting  on  to  the  rod,  except  by  going 
clear  round  the  house,  or  passing  over  the  top. 
Evidently,  in  attempting  the  latter,  the  force  of  the 
charge  passed  into  the  building  ere  it  could  reach 
the  rod.  Hence  the  destruction  which  followed. 

This  instance  is  thus  noticed  in  an  editorial  of 
the  Say  brook  Mirror,  June  24,  1852  : — 

“  Singular  Freah  of  Lightning. — During  the  shower 
on  Wednesday  of  last  week,  the  house  of  A.  J. 
Platt,  of  Deep  Eiver,  was  struck,  doing  considera¬ 
ble  damage.  It  appeared  to  be  what  is  called  an 
upward  stroke^  passing  up  the  door-casing  of  the  hall- 


DAMAGED  BY  LIGHTNING. 


169 


door,  knocking  off  the  plastering  in  the  hall  and 
parlor,  and  thence,  through  the  hall,  the  side  of  the 
house,  where  the  wing  connects,  to  the  corner  of  the 
wing,  passing  down  on  a  pillar ;  and  also  at  another 
point  into  the  sink,  knocking  off  splinters,  and  loosen¬ 
ing  the  clapboards  in  various  places. 

“  A  singular  feature  is,  that  the  house  was 
guarded  by  a  lightning  rod  attached  to  each  chim¬ 
ney,  running  down  the  roof,  and  from  thence  to  the 
ground ;  and  there  is  abundant  evidence  that  the 
electric  current,  in  its  progress,  passed  within  some 
six  or  seven  feet  of  this  rod,  and  that  the  protection 
which  it  is  claimed  to  give,  was  of  no  avail  in  this 
instance.  The  rod  is  one  of  those  put  up  by  Dr. 
Minor,  who  has  also  put  up  several  in  this  village, 
and  we  would  like  to  hear  his  explanation  of  their 
inefficiency  in  this  case,  as  he  claims  them  as  superior 
to  any  other. 

That  there  is  sure  protection  in  a  conductor,  we 
believe,  and  it  would  be  well  for  those  about  to 
procure  this  safeguard,  to  ascertain  that  they  procure 
the  best  article,  and  have  them  rightly  put  up.  It 
is  a  matter  which  is  not  lightly  to  be  passed  over, 
where  the  lives  of  people  and  property  are  at 
stake.” 

In  so  long  a  period  as  three-quarters  of  a  cen¬ 
tury,  it  is  not  to  be  expected  that  no  casualties 
should  occur,  either  from  a  defective  application  of 
the  conductor,  or  from  an  explosion  falling  on  some 
part  of  the  building  at  a  distance  from  the 
ductor. 

8 


110 


PRECAUTIONS  WHEN  EXPOSED  TO 


Precautions  when  exposed  to  the  action  of  Thunder stcyrms. 

From  circumstances  of  almost  constant  inquiry 
attending  thunderstorms,  it  is  impossible  to  witness 
one  without  some  feelings  of  personal  danger;  in 
this  case  attention  to  the  following  observations  may 
often  be  of  service  in  relieving  the  mind  from  un¬ 
necessary  fear,  or  in  suggesting  the  necessary  steps 
to  be  taken  for  the  prevention  of  accident. 

The  precautions  generally  offered  b}^  writers  on 
electricity,  as  necessary  for  the  safety  of  those  who 
are  exposed  to  the  action  of^a  thunderstorm,  may  be 
thus  enumerated  :  “  shelter  should  not  be  taken  under 
trees,  hedges,  &c.,  for,  should  they  be  struck,  such 
situations  are  particularly  dangerous ;  at  the  same 
time  a  person  is  much  safer  at  about  thirty  or  forty 
feet  from  such  objects  than  at  a  greater  distance,  as 
they  are  likely  to  operate  as  conductors.  Large  por¬ 
tions  of  water  also  ought  to  be  carefully  avoided  if 
possible,  and  even  streamlets  that  may  result  from 
recent  rain ;  these  are  good  conductors,  and  the  height 
of  a  human  being  connected  with  them,  may  some¬ 
times  determine  the  course  of  the  lightning.  In  a 
house  the  safest  situation  is  considered  to  be  the 
middle  of  the  room ;  and  this  situation  may  be  ren¬ 
dered  still  more  secure  by  standing  on  a  glass-legged 
stool ;  but,  as  such  an  article  is  not  in  the  possession 
of  many  people,  a  hair  mattress,  or  a  thick  woollen 
hearth-rug  makes  a  very  good  substitute.  It  is  very 
injudicious  to  take  refuge,  as  some  persons  do,  in  the 


THE  ACTION  OF  THUNDERSTORMS.  171 

cellar  during  a  thunderstorm,  since  the  discharge  is 
often  found  to  be  from  the  earth  to  the  clouds,  and 
many  instances  are  recorded  of  buildings  that  were 
struck  having  sustained  the  greatest  injury  about  the 
basement  story.  But,  whatever  situation  is  chosen, 
the  greatest  care  should  be  taken  to  avoid  going 
near  the  fire-place,  since  the  chimneys  are  most  likely 
to  attract  the  fluid,  and  even  if  there  be  no  fire  in 
the  grate,  at  the  time,  it  should  be  remembered  that 
soot  is  a  powerful  conductor.  The  same  caution  is 
necessary  with  respect  to  all  large  metallic  surfaces ; 
gilt  furniture,  bell  wires,  &c.”* 

Construction  of  Lightning  Rods  applied  to  Buildings. 
■) 

But  the  most  important  and  useful  application 
that  has  ever  yet  been  made  of  the  discoveries  of  the 
electrician  is  in  the  method  of  securing  buildings, 
ships,  &c.,  from  effects  of  lightning.  To  the  in¬ 
genuity  of  Dr.  Franklin  the  world  is  indebted  for 
this  invention,  as  well  as  for  his  discovery  of  the 
identity  of  lightning  and  common  electricity ;  and 
these  are  justly  considered  two  of  the  grandest  dis¬ 
coveries  of  last  century. 

As  this  subject  is  of  the  utmost  importance,  we 
shall  here  quote  the  opinions  of  many  of  the  most 
eminent  electricians  who  have  written  on  the  subject 
of  lightning  conductors.  Mr.  Cavallo,  speaking  of 
the  proposal  of  Dr.  Franklin,  which  we  have  just 


*  London  EncyclopcBdia,  vol.  8,  p.  59. 


\12 


CONSTRUCTION  OF  LIGHTNING  RODS 


noticed,  remarks  that  the  reasonableness  and  truth 
of  such  an  assertion  has  been  confirmed  by  numer¬ 
ous  facts,  and  the  practice  of  raising  such  conductors 
has  been  found  exceedingly  useful,  particularly  in 
hot  climates,  where  thunderstorms  are  very  frequent, 
and  the  damage  occasioned  by  the  same  too  often 
experienced. 

“  In  regard  to  the  construction  of  such  conduc¬ 
tors,  there  have  been  some  controversies  among  elec¬ 
tricians  ;  and  the  most  advantageous  manner  of  using 
them  has  not,  without  a  great  many  experiments, 
and  but  very  lately,  been  ascertained.”  Some  phi¬ 
losophers  have  asserted  that  such  conductors  should 
terminate  in  an  obtuse  end,  that  they  might  the  less 
invite  the  lightning  from  the  clouds ;  for  such  an 
end  will  not  attract  electricity  from  so  great  a  dis¬ 
tance  as  a  sharp  point.  But  other  philosophers  have 
thought  a  pointed  termination  to  be  much  preferable 
to  an  obtuse  one  ;  and  their  assertion  seems,  on  the 
following  accounts,  to  be  better  founded. 

“  A  sharp-pointed  conductor,  it  is  true,  will  attract 
electricity  from  a  greater  distance  than  one  with  an 
obtuse  point,  but  at  the  same  time  will  attract  and 
conduct  it  very  gradually,  or  rather  by  a  continued 
stream,  in  which  manner  a  remarkably  small  con¬ 
ductor  is  capable  of  conducting  a  very  great  quantity 
of  electricity ;  whereas  an  obtusely  terminated  con¬ 
ductor  attracts  the  electricity  in  a  full  separate  body, 
or  explosion,  by  which  it  is  often  made  red  hot, 
melted,  and  even  exploded  in  smoke,  and  by  such  a 
quantity  as  perhaps  would  not  have  at  all  affected  it, 
if  it  had  been  sharply  pointed. 


APPLIED  TO  BUILDINGS. 


173 


“  A  sharp‘pointed  conductor  certainly  invites  the 
matter  of  lightning  easier  than  an  obtuse  one  ;  but 
to  invite,  receive,  and  conduct  it  in  small  quantities, 
never  endangers  the  conductor;  and  the  object  of 
fixing  a- conductor  to  a  house,  is  to  protect  the  house 
from  the  effects  of,  and  not  the  conductor  from  trans¬ 
mitting,  the  lightning. 

“It  is  an  observation  much  in  favor  of  sharp- 
pointed  conductors,  that  such  steeples  of  churches, 
and  edifices  in  general,  as  are  terminated  by  pointed 
metallic  ornaments,  have  very  seldom  been  known 
to  be  struck  by  lightning;  whereas  others  that  have 
flat  terminations  and  have  a  great  quantity  of  metal 
in  a  manner  insulated  on  the  top,  are  often  struck  ; 
and  it  is  but  seldom  that  they  escape  without  great 
damage. 

“Besides  these  considerations  a  sharp-pointed 
conductor,  by  the  same  property  of  attracting  elec¬ 
tricity  more  readily  than  an  obtusely  terminating  one, 
may  prevent  a  stroke  of  lightning,  which  the  latter 
is  incapable  of  doing. 

“  A  conductor,  therefore,  to  guard  a  building, 
should  be  fastened  to  the  wall,  not  by  iron  cramps, 
but  by  pieces  of  wood.  If  this  conductor  were 
quite  detached  from  the  building,  and  supported  by 
wooden  -  posts  the  distance  of  one  or  two  feet  from 
the  wall,  it  would  be  much  better.  The  upper  end 
of  the  conductor  should  be  terminated  in  a  pyra¬ 
midal  form,  with  the  edges,  as  well  as  the  point,  very 
sharp ;  and  if  the  conductor  be  of  iron,  it  should  be 
gilt.  This  sharp  end  should  be  elevated  above  the 
highest  part  of  the  building  (as  above  a  stack  of 


174 


CONSTRUCTION  OF  LIGHTNING  RODS 


cliimneys,  to  which  it  may  be  fastened)  at  least  five 
or  six  feet.  The  lower  end  should  go  five  or  six  feet 
into  the  ground,  and  in  a  direction  leading  from  the 
foundation  ;  or  it  would  be  better  to  connect  it  with 
the  nearest  piece  of  water,  if  any  be  at  hand.  If 
this  conductor,  on  account  of  the  difficulty  of  adapt¬ 
ing  it  to  the  form  of  the  building,  cannot  conven¬ 
iently  be  made  of  one  rod,  then  care  should  be 
taken,  that,  where  the  pieces  meet,  they  be  made  to 
come  in  as  perfect  a  contact  with  one  another  as 
possible ;  for  electricity  finds  considerable  obstruction 
where  the  conductor  is  interrupted. 

“  In  ships  a  chain  has  often  been  used  for  this 
purpose,  which,  on  account  of  its  pliableness,  has 
been  found  very  convenient,  and  easy  to  be  managed 
among  the  rigging  of  the  vessel ;  but  as  the  electri¬ 
city  finds  a  great  obstruction  in  going  through  the 
several  links,  so  that  chains  have  been  actually 
broken  by  the  lightning,  their  use  is  now  almost  en¬ 
tirely  laid  aside.” 

Mr.  Cavallo  gives  with  cordial  approbation,  the 
following  extract  from  the  Earl  of  Stanhope’s  learned 
work  on  electricity.  As  requisites  for  the  proper  con¬ 
struction  of  conducting  rods  for  the  preservation  of 
buildings  from  the  effects  of  lightning  he  directs,  (1.) 
“  That  the  rods  be  made  of  such  substances  as  are 
the  best  conductors  of  electricity.  (2.)  That  the  rods 
be  uninterrupted  and  perfectly  continuous.  (3.)  That 
they  be  of  sufficient  thickness.  (4.)  That  they  be 
perfectly  connected  with  the  main  rod.  (5.)  That 
the  upper  extremity  of  the  rods  be  as  acutely  pointed 


APPLIED  TO  BUILDINGS. 


175 


as  possible.  (6.)  That  it  be  very  finely  tapered.  (7.) 
That  they  be  prominent.  (8.)  That  each  rod  be 
carried  in  the  shortest  convenient  direction,  from  the 
point  at  its  upper  end  to  the  main  rod.  (9.) 
That  there  be  neither  large  nor  prominent  bodies  of 
metal  upon  the  top  of  the  building  proposed  to  be 
secured,  but  such  as  are  connected  with  the  conduc¬ 
tor  by  some  proper  metallic  communication.  (10.) 
That  there  be  a  sufficient  number  of  high  and  pointed 
rods.” 

A  very  interesting  report  on  the  subject  of 
lightning  conductors,  was  presented  to  the  Eoyal 
Academy  of  Sciences  by  M,  Gay  Lussac.  The  in¬ 
formation  contained  in  it  may  be  regarded  in  many 
respects  as  the  most  perfect  we  possess  on  the  sub¬ 
ject.  In  this  paper  we  learn  “  that  the  electric  matter 
tends  always  to  spread  itself  over  conductors,  and  to 
assume  a  state  of  equilibrium  in  them,  and  becomes 
divided  among  them  in  proportion  to  their  form  and 
principally  to  their  extent  of  surface ;  and  that  hence 
a  body  that  is  charged  with  the  fluid  being  in  com¬ 
munication  with  the  immense  surface  of  the  earth, 
will  retain  no  sensible  portion  of  it.” 

Gay  Lussac  defines  a  lightning  rod  “  to  be  a  con¬ 
ductor  which  the  electric  matter  prefers  to  the  sur¬ 
rounding  bodies,  in  order  to  reach  the  ground,  and 
expand  itself  through  it,  and  should  descend  without 
any  divisions  or  breaks  in  its  length  into  water  or 
moist  ground.  When  a  conductor  has  any  breaks 
in  it,  or  is  not  in  perfect  communication  with  a  moist 
soil,  the  lightning  having  struck  it,  flies  from  it  to 


176  ’  CONSTRUCTION  OF  LIGHTNING  RODS 

some  neighboring  body,  or  divides  itself  between 
the  two,  in  order  to  pass  more  rapidly  into  the  earth. 

“Tlie  most  advantageous  form  that  can  be  given 
to  the  extremity  of  a  conductor,  is  that  of  a  sharp 
cone  ;  and  as  iron  is  very  liable  to  rust  by  the  action 
of  air  and  moisture,  the  point  of  the  stem  would 
soon  become  blunt ;  and  therefore,  to  prevent  it,  a 
portion  of  the  top  should  be  composed  of  a  conical 
stem  of  brass  or  copper,  gilt  at  its  extremity ;  and  the 
higher  it  is  elevated  in  the  air,  other  circumstances 
being  equal,  the  more  its  efficacy  will  be  increased.” 

“  The  rod  should  be  supported  parallel  to  the 
roof,  at  about  six  inches  distance  from  it,  by  forked 
stanchions ;  and  after  turning  over  the  cornice  of 
the  building  without  touching  it,  should  be  brought 
down  the  wall.  In  a  dry  soil,  or  on  a  rock,  the 
trench  to  receive  the  conductor  should  be  at  least 
twice  as  long  as  that  for  a  common  soil,  and  even 
longer,  if  thereby  it  be  possible  to  reach  moist  ground. 
Should  the  situation  not  admit  of  the  trench  being 
much  increased  in  length,  others  in  a  transverse  di¬ 
rection  should  be  made,  in  which  the  lower  extremi¬ 
ties  of  the  conductor  are  to  be  placed.  In  general, 
the  trench  should  be  made  in  the  dampest,  and  con¬ 
sequently,  lowest  spot,  near  the  building,  and  the 
water  gutters  made  to  discharge  their  waters  over  it, 
so  as  to  keep  it  always  moist.  Too  great  precaution 
cannot  be  taken  to  give  the  lightning  a  ready  pass¬ 
port  to  the  ground,  for  it  is  chiefly  on  this  that  the 
efficacy  of  a  conductor  depends.”* 


*  London  Encyclopcedia,  vol.  viii.,  p.  61 . 


APPLIED  TO  BUILDINGS. 


177 


The  importance  of  insulating  lightning  conduct¬ 
ors,  seems  to  have  been  better  understood  by  electri¬ 
cians,  than  the  methods  by  which  it  is  effected. 
Some  philosophers  observe,  that  the  insulation  may 
be  effected  by  “having  the  iron  fastenings  of  the 
rod  to  the  wall  large  and  blunt,  and  covered  with 
two  or  three  folds  of  woollen  cloth  steeped  in,  and 
covered  with  melted  pitch:”*  others,  “that  the  con¬ 
ductor  should  be  fastened  to  the  wall  not  by  iron 
cramps,  but  by  pieces  of  wood.  If  the  conductor 
were  quite  detached  from  the  building,  and  sup¬ 
ported  by  wooden  posts  the  distance  of  one  or  two 
feet  from  the  wall,  it  would  be  much  better.”f 
While  others,  still,  have  thought  that  a  more  perfect 
insulation  was  secured  by  India-rubber,  or  by  pass¬ 
ing  the  rod  through  the  necks  of  glass  bottles,  and 
more  recently,  through  glass  thimbles  or  rings,  cut 
vertically  through  the  centre.  If  insulation  is  effected 
by  thus  passing  the  conductor  through  glass,  it  is 
much  better  that  the  glass  rings  be  in  two  semi¬ 
circular  parts  than  to  have  it  whole  ;  for  experience 
has  proved,  that  it  is  far  less  likely  to  be  broken  by 
the  sudden  heat  and  violent  expansion  of  air  which 
always  precedes  the  electric  fluid  in  a  lightning  dis¬ 
charge.  If  the  lightning  rod  could  pass  round  or 
over  glass  caps,  as  the  telegraphic  wires  do,  it  would 
be  better  still.  With  such  a  mode  of  insulation,  no 
possible  harm  can  result  to  the  insulator,  however 
powerful  the  explosion. 

*  Encyclopcedia,  vol.  viii.,  p.  647. 

f  London  Encyclovcedia,  vol.  viii.,  p.  61. 

8^ 


178 


CONSTRUCTION  OF  LIGHTNING  RODS 


We  close  our  remarks  on  the  construction  of 
lightning  conductors,  with  a  quotation  from  Pro¬ 
fessor  Sturgeon,  Superintendent  and  Lecturer  of  the 
Eoyal  Victoria  Glallery  of  Practical  Science,  Man¬ 
chester,  formerly  Lecturer  on  Experimental  Philo¬ 
sophy  at  the  Hon.  East  India  Company’s  Military 
Academy,  Addiscombe,  &c.,  &c.,  &c. 

“  The  subject  of  lightning  conductors  is  a  branch 
of  practical  electricity  of  exceedingly  high  interest, 
and  demands  the  contemplation  of  the  most  pro¬ 
found  electricians.  Hitherto,  however,  little  more 
has  been  attended  to  than  the  erection  of  a  pointed 
rod  of  iron,  without  regard  to  situation,  altitude, 
diameter,  inferior  termination,  or  any  of  those  theo¬ 
retical  points  essential  to  the  efficacy  and  protection 
of  the  conductors,  so  as  to  render  it  a  safeguard  to 
persons  and  property  against  the  ‘  most  formidable 
element  of  nature.’ 

“  Franklin,  the  inventor  of  lightning  conductors, 
first  proposed,  ‘  for  protecting  houses,  churches, 
ships,  &c.,  from  the  stroke  of  lightning,  to  fix  on  the 
highest  parts  of  these  edifices  upright  rods  of  iron, 
made  sharp  as  a  needle,  and  gilt,  to  prevent  rusting ; 
and  from  the  foot  of  these  rods,  a  wire  down  the  out¬ 
side  of  the  building  into  the  ground^  or  round  one 
of  the  shrouds  of  d  ship,  and  down  her  side,  till  it 
reaches  the  water.  Would  not  these  pointed  rods 
probably  draw  the  electrical  fire  silently  out  of  a 
cloud  before  it  came  near  enough  to  strike,  and 
thereby  secure  us  from  that  most  sudden  and  terri¬ 
ble  mischief?  ’  ” 


APPLIED  TO  BUILDINGS.  iVO 

This  philosopher,  however,  subsequently  recom¬ 
mended  continuous  iron  rods,  of  about  half  or  three- 
quarters  of  an  inch  diameter ;  which  he  said  “  may 
be  fastened  to  the  wall,  chimney,  &c.,  with  staples 
of  iron.  The  lightning  will  not  leave  the  rod, 
a  good  conductor,  to  pass  into  the  wall,  a  bad  con¬ 
ductor,  through  the  staples.  It  would  rather,  if  any 
were  in  the  wall,  pass  out  of  it  into  the  rod,  to  get 
more  readily  by  that  conductor  into  the  earth. 

“If  the  building  be  very  large  and  extensive, 
two  or  more  rods  may  be  placed  at  different  parts, 
for  greater  security. 

“  Small  ragged  parts  of  clouds  suspended  in  the 
air  between  the  great  body  of  clouds  and  the  earth, 
often  serve  as  partial  conductors  for  the  lightning, 
w  hich  proceeds  from  one  of  them  to  another,  and  by 
their  help  comes  within  the  striking  distance  of  the 
earth  or  a  building.  It  therefore  strikes  through 
those  conductors  a  building  that  would  otherwise  be 
out  of  the  striking  distance. 

“Long  sharp  points  communicating  with  the 
earth,  and  presented  to  such  parts  of  clouds,  draw 
silently  from  them  the  fluid  they  are  charged  with  ; 
these  parts  of  clouds  are  then  attracted  to  the  main 
cloud,  and  may  leave  the  distance  so  great  as  to  be 
beyond  the  reach  of  striking. 

“  It  is  therefore  that  we  elevate  the  upper  end  of 
the  rod  six  or  eight  feet  above  the  highest  part  of 
the  building,  tapering  it  gradually  to  a  fine  sharp 
point,  gilt  to  prevent  its  rusting.  Thus  the  pointed 
rod  either  prevents  a  stroke  from  the  cloud,  or  if  a 


180 


CONSTRUCTION  OF  LIGHTNING  RODS 


stroke  be  made,  conducts  it  to  tbe  earth  with  safety 
to  the  building. 

“  The  lower  end  of  the  rod  should  enter  the  earth 
so  deep  as  to  come  at  the  moist  part,  and  if  bent  un¬ 
der  the  surface  so  as  to  go  in  a  horizontal  line  six  or 
eight  feet  from  the  wall,  and  then  bent  again  down¬ 
wards  three  or  four  feet,  it  will  prevent  damage  to 
any  of  the  stones  of  the  foundation.” 

Of  these  instructions  of  the  celebrated  Franklin, 
Prof.  Sturgeon  remarks,  that  “had  he  recommended 
copper  rods  instead  of  iron,  and  directed  them  to  be 
kept  clear  of  the  building  instead  of  being  fastened 
to  the  walls  with  staples  of  iron,  perhaps  no  better 
instructions  could  have  been  given  ;  as  far,  at  least, 
as  an  individual  rod  is  concerned.  But  besides  the 
injury  that  buildings  may  receive  from  a  flash  of 
lightning  striking  a  conductor  fixed  close  to  the  slates 
and  masonry,  from  lateral  explosions,  a  conductor 
consisting  of  a  single  branch  only  might  be  the 
means  of  drawing  down  destruction  to  some  parts 
of  the  building  before  the  lightning  reached  that 
conductor.  For,  were  the  lightning  cloud  on  one 
side  of  the  building,  and  the  conductor  on  the  other, 
the  lightning  would  neither  go  round  nor  over  the 
house  to  arrive  at  the  conductor,  unless  it  met  with 
greater  resistance  in  a  direct  path,  and  as  the  desti¬ 
nation  of  lightning  is  frequently  a  greater  distance 
from  the  cloud,  and  its  path  considerably  oblique,  it 
is  possible  that  some  part  of  its  path  might  be 
through  a  part  of  the  building  before  it  arrived  at  a 
lightning  rod  which  formed  another  part  of  its  path. 


APPLIED  TO  BUILDINGS. 


181 


“  Cases  of  this  kind  have  occurred,  and,  conse¬ 
quently,  may  possibly  occur  again  under  similar  cir¬ 
cumstances;  therefore  it  seems  to  me  that  unless 
lightning  conductors  be  properly  placed,  and  of 
proper  materials  and  dimensions,  they  may  be  the 
means  of  causing  the  most  destructive  consequences 
to  those  buildings  they  were  intended  to  protect.  It 
is  very  seldom  indeed  that  a  flash  of  lightning  ‘proceeds 
in  a  vertical  path  ;  perhaps  never. 

“  I  never  yet  saw,  or  heard  of,  a  vertical  dis¬ 
charge  of  lightning ;  they  are  frequently  very  ob¬ 
lique  indeed.  The  lightning  which  damaged  Saint 
Michael’s  Church,  at  Liverpool,  last  year,  was  an  ob¬ 
lique  discharge,  and  struck  the  bronze  cross  at  the 
top  of  the  spire,  several  feet  from  its  top. 

“  There  is  such  a  display  of  ignorance  in  the  erec¬ 
tion  of  tall  spires,  that  it  is  almost  a  miracle  that  the 
whole  of  them  are  not  destroyed  by  lightning.  The 
upper  clamps  and  strings  of  lead,  the  former  uni¬ 
formly  placed  at  intervals  from  each  other,  and  the 
latter  wantonly  poured  into  the  crevices  of  the  ma¬ 
sonry,  render  the  spire  a  complete  chain  of  alternate 
links  of  metal  and  masonry  from  top  to  bottom :  the 
former  inviting  the  lightning  to  the  edifice,  and  the 
latter  offering  facilities  for  the  most  destructive  ex¬ 
plosions.  From  this  very  arrangement  of  the  mate¬ 
rials  in  the  steeples  of  Saint  Michael’s  and  Saint  Mar¬ 
tin’s  at  Liverpool,  and  in  the  steeple  of  Brixton 
Church,  have  these  three  steeples  been  shattered  by 
lightning.  If  such  modes  of  building  tall  spires  be 
indispensable  to  protect  them  from  the  power  of  the 


182 


CONSTRUCTION  OF  LIGHTNING  RODS 


wind,  conductors  are  quite  as  indispensable  to  pro¬ 
tect  them  from  lightning.  Three  rods  (copper  best) 
at  equal  distances  from  one  another,  from  the  top  of 
the  spire  to  the  ground,  and  united  at  the  top,  and 
by  one  or  two  bands  below,  would  secure  each  spire 
from  lightning  on  whichever  side  it  approached. 

“Lightning  rods  however  numerous  about  a 
building,  should  have  a  general  metallic  union ;  they 
then  form  a  system  of  conductors  in  which  the  force 
of  the  lightning  would  be  divided,  whichever  branch 
was  struck.  I  have  a  beautiful  experiment  to  offer 
to  your  notice,  illustrative  of  this  fact. 

‘  The  apparatus  represented  by  fig.  18,  consists 

4^ 


Fig.  18. 


of  a  series  of  iron  wire  chains,  so  connected  as  to 
form  a  system  of  conductors  of  many  branches. 
The  chains  hang  vertically  from  a  horizontal  brass 
wire,  and  their  lower  ends  rest  on  a  sheet  of  tin-foil. 
The  brass  wire  first  receives  the  jars,  and  the  tin-foil 
carries  it  from  the  chains  to  the  outside  of  the  jar.  The 
electric  fluid,  whilst  traversing  this  circuit,  illumin- 


APPLIED  TO  BUILDINGS. 


183 


ates  every  chain  in  the  system  to  the  same  extent, 
showing  that  it  is  equally  divided  amongst  them  ; 
and  had  there  been  ten  thousand  such  channels,  it 
would  have  divided  itself  amongst  the  whole  of  them. 
This  experiment  shows  two  or  more  interesting  facts. 
It  proves  that  the  iron  scintillates  at  every  link  by 
an  electric  discharge  through  a  chain  of  that  metal ; 
and  these  scintillations  discover  to  us  that  the  fluid 
occupies,  and  passes  through,  every  channel  in  the 
circuit.”* 

That  we  may  not  omit  any  information  on  the 
subject  that  may  be  deemed  useful,  we  shall  add 
Mr.  Morgan’s  method  of  preventing  all  possible  dan¬ 
ger.  The  plan  which  Mr.  Morgan  proposes  is,  that, 
whilst  a  house  is  being  built,  “the  foundation  of  each 
partition  wall  should  be  laid  on  a  strip  of  lead,  or 
a  strip  should  be  fastened  to  the  sides  of  these  parti¬ 
tion  walls.  The  strips  should  be  two  inches  wide, 
and  at  least  a  quarter  of  an  inch  thick,  and  closely 
connected  with  each  other.  A  perpendicular  strip, 
on  each  side  of  the  house,  should  rise  from  the  con¬ 
ductors  to  the  surface  of  the  ground;  whence  a  strip 
should  be  continued  round  the  house,  and  carefully 
connected  with  water-pipes,  &c.  The  strips  on  the 
sides  of  the  house  should  then  be  continued  to  the 
roof,  which  ought  to  be  guarded  in  the  same  manner 
as  the  foundation.  The  top  should  be  surrounded 
by  a  strip,  which  should  be  connected  with  every 
edge  and  prominence,  and  continued  to  the  sum¬ 
mit  of  each  separate  chimney.”  It  is  particularly 

*  Sturgeon's  Lectures  on  Electricity. 


184 


PRACTICAL  DEDUCTIONS. 


necessary  to  guard  the  chimneys;  for  Mr.  Morgan 
mentions  a  case  in  which  a  house  that  had  been 
guarded  in  most  respects,  according  to  the  preceding 
directions,  except  that  the  chimneys  were  unpro¬ 
tected,  was  struck  with  lightning,  which  entered  by 
one  of  the  chimneys ;  here  it  spent  its  fury  ;  but  the 
chimneys  falling  on  the  roof  did  considerable  damage. 

All  electricians  agree  “  that  security  is  rendered 
more  perfect  by  having  every  piece  of  metal  on  the 
^  roof  in  metallic  connection  with  the  conductor,  and 
continuous  strips  of  lead  built  into  every  wall,  and 
connected  to  one  another  by  horizontal  strips  com¬ 
municating  also  with  the  conductor.”* 

The  only  objection  to  this  method  of  protection 
is  the  expense.  But  even  this  is  mainly  obviated, 
by  having  the  conductors  so  constructed  as  to  run 
the  whole  length  of  the  building  on  the  ridge,  with 
branches  to  the  chimneys,  and  duly  elevated  above 
them  ;  and,  in  case  of  small  buildings,  continuing  the 
main  rod  on  the  ridge  over  the  roof,  down  the  oppo¬ 
site  diagonal  corners  of  the  building  to  the  ground  ; 
and  if  the  building  is  large,  by  having  rods  ex¬ 
tend  from  the  main  rod  on  the  ridge  over  each  end 
of  the  roof,  down  the  four  corners ;  and  having  all 
the  conductors  united  to  one  another  by  a  perfect 
metallic  union. 

Practical  Deductions. 

1.  The  conductor  should  be  made  of  good  con¬ 
ducting  substance. 


*  Encyclopcedia  Britannica,  vol.  viii.  p.  647. 


PRACTICAL  DEDUCTIONS. 


185 


2.  It  should  have  great  electrical  capacities ;  a 
square  rod  requires  less  metal  than  a  round  rod. 

3.  It  should  be  perfectly  continuous,  e.,  it 
should  have  no  breaks  in  the  connections ;  no  links 
or  hooks,  but  a  perfect  metallic  union  of  every  part. 
If  a  person  should  think  that  a  ring  of  zinc  near 
these  connections,  improves  the  appearance  of  the 
rod,  there  can  be  no  objection,  though  there  is  no 
other  possible  advantage. 

4.  It  should  be  insulated  from  the  building  to  be 
protected,  except  from  such  masses  of  metal  as  are 
likely  to  offer  other  lines  of  discharge. 

5.  It  should  have  numerous  lateral  points  : — 
one  in  six  or  seven  feet  will  answer.  The  more  nu¬ 
merous  these  points  are,  the  greater  the  conducting 
power  of  the  rod.  Besides,  these  lateral  points  pro¬ 
vide  for  an  oblique  discharge,  each  being  as  good  a 
receiving  point  as  the  higher  point  at  the  chimney 
or  other  prominences.  They  also  guard  against  a 
lateral  explosion,  or  a  division  of  the  charge,  which 
is  liable  to  happen  in  case  the  rod  is  overcharged, 
especially  if  it  be  fastened  to  the  house  with  pointed 
staples  ;  and  in  case  of  an  upward  stroke,  the  electric 
fluid  being  discharged  at  so  many  different  points, 
no  harm  can  possibly  occur. 

6.  Its  upper  extremity  should  project  freely  into 
the  air;  should  be  pointed  ;  and  may  be  triangular, 
somewhat  similar  to  a  bayonet ;  or  it  may  have  seve¬ 
ral  branches.  The  only  scientific  advantage  in 
having  a  branching  head  or  point  for  the  superior 
termination,  is  this :  all  the  points  are  not  likely  to 


186 


PRACTICAL  DEDUCTIONS. 


become  blunt  at  the  same  time.  Some  have  sup¬ 
posed  that  the  point  should  be  magnetized  ;  and  little 
needles,  called  magnets^^  have  sometimes  been 
added.  But  it  is  difficult  to  see  the  practicability  of 
this  recent  discovery ;  for  most  are  aware,  that  mag¬ 
netized  iron  or  steel  soon  loses  its  magnetic  influ¬ 
ence.  But,  is  there  any  truth  or  science  in  this 
application  of  magnetism?  If  there  is^  we  con¬ 
fess,  that  we  have  not  been  able  to  discover  it  in 
any  experiments  in  the  laboratory  ;  neither  can  we 
learn  that  the  subject  has  even  been  mentioned  by 
any  writer  whatever^  on  the  subject  of  electricity. 

7.  The  upper  termination  should  be  plated  with 
silver  or  gold,  to  prevent  corrosion. 

8.  Every  branch  rod  running  to  chimneys,  and 
other  prominences,  should  have  a  perfect  metallic 
union  with  the  main  rod. 

9.  In  cases  where  metallic  vane-spindles,  or  other 
points  exist,  the  conductor  may  commence  from 
these,  and  should  be  applied  immediately  to  the  part 
to  be  protected,  and  not  at  a  distance  from  it ;  and 
should  be  so  applied,  that  a  discharge  of  lightning 
falling  on  the  general  mass,  could  not  possibly  find 
its  way  to  the  ground  through  the  building  by  any 
circuit  of  which  the  conductor  did  not  form  a  part ; 
that  is  to  say,  the  conductor  should  be  so  carried 
over  the  several  parts  of  the  building,  that  the  dis¬ 
charge  could  not  fall  upon  it  without  being  trans¬ 
mitted  safely  by  the  conductor.  Hence,  the  rod 
should  run  along  the  whole  length  of  the  ridge,  and 


CONCLUDING  OBSERVATIONS. 


187 


down  to  the  ground,  at  least  on  two  sides  of  the  build¬ 
ing.  If  the  building  is  large,  it  should  run  down  on 
each  corner. 

10.  Every  conductor  running  to  the  ground, 
should  terminate  sufficiently  beneath  the  surface,  to 
insure  moisture  in  the  dryest  part  of  the  season.  If 
circumstances  permit,  it  should  connect  with  a  spring 
of  water,  a  drain,  or  some  other  conducting  channel. 

Concluding  Observations. 

We  have  seen  that  electricity  is,  from  various 
causes,  generated  and  set  free  in  our  atmosphere ; 
and  that  individual  clouds,  and  masses  of  clouds,  are 
often  highly  charged  with  electricity,  and  insulated 
by  the  surrounding  air.  The  earth  and  the  sea  are 
good  conductors  of  electricity ;  and,  generally  speak¬ 
ing,  their  natural  electricity  is  undisturbed.  The 
attraction,  therefore,  of  the  electricity  of  the  clouds 
for  the  opposite  electricity  in  the  earth  or  the  sea, 
may  become  so  powerful  as  to  break  through  the 
resisting  medium  which  intervenes.  If  the  clouds 
are  above  a  mountain,  or  rising  ground,  this  dis¬ 
charge  of  electric  matter  into  the  earth  is  often  at¬ 
tended  with  the  fusion  of  portions  of  the  rocks  which 
crown  these  exposed  summits.  If  a  tree  stands  in 
the  stratum  of  air  through  which  the  cloud  discharges 
itself,  the  lightning  passes  through  it,  cleaving,  and 
bursting,  and  damaging  it  in  its  passage.  If  a  house 
obstructs  its  path,  the  electricity  descends  through 


188 


CONCLUDING  OBSERVATIONS. 


its  walls,  and  gilded  pictures,  and  finds  out  any 
matter,  whether  organized  or  unorganized,  living  or 
dead,  which  is  placed  near  its  path,  and  is  capable 
of  advancing  it  on  its  rapid  and  breathless  errand  to 
the  earth.  If  a  living  animal  grazing,  or  a  human 
being  walking  in  an  open  field,  intervenes  between 
the  overcharged  cloud  and  the  ground,  the  one  or 
the  other  will  become  the  chosen  path  of  this  irre¬ 
sistible  foe.  If  a  ship  floats  under  an  electrified 
canopy  of  vapor,  it  has  less  chance  of  escape  than 
the  tree,  the  house,  or  the  living  being. 

The  only  terms  upon  which  we  can  meet  this 
relentless  enemy,  is  an  humble  admission  of  its  su¬ 
preme  ’and  irresistible  power,  and  a  resolution  to 
give  it  the  freest  and  the  fullest  passport  through 
our  territory.  We  must  supply  it,  in  short,  with  a 
railway  of  metal,  the  only  species  of  road  upon 
which  it  can  travel  with  a  suitable  speed  and  a  harm¬ 
less  intention.  The  moment  it  ceases  to  find  a  con¬ 
ducting  body,  it  begins  its  devastation  among  im¬ 
perfect  or  non-conducting  substances,  till  it  again 
gets  into  a  safe  and  easy  path. 

Truly  was  it  an  auspicious  period  when  Df. 
Franklin  raised  electricity  to  the  dignity  of  a  science, 
and  connected  it  with  that  tremendous  agency 
which  had  so  often  terrified  the  moral,  and  con¬ 
vulsed  the  physical  world.  The  thunderbolt  had  fre¬ 
quently  descended  from  heaven  upon  its  victims ;  but 
mortal  genius,  though  it  comprehended  not  the  most 
perfect  method  of  constructing  an  electrical  machine, 
or  a  lightning  conductor,  had  now  learned  to  bring 


CONCLUDING  OBSERVATIONS. 


189 


it  down  in  chains,  to  disarm  its  fury,  and  to  convert 
it  into  a  useful,  and  even  a  friendly  element. 

After  a  successful  test  of  the  utility  of  lightning 
conductors  on  the  house  of  Mr.  West  in  Philadelphia, 
with  a  mind  quick  to  perceive  and  a  heart  true  to  a 
sense  of  justice,  how  natural  the  congratulations  of 
Mr.  Kinersley  to  Dr.  Franklin.  “  Sir,  I  most  heartily 
congratulate  you  on  the  pleasure  you  must  experi¬ 
ence  on  finding  your  great  and  well-grounded  expec¬ 
tations  so  far  fulfilled.  May  this  method  of  security 
from  the  destructive  violence  of  one  of  the  most 
awful  powers  of  nature,  meet  with  such  further  suc¬ 
cess,  as  to  induce  every  good  and  grateful  heart  to 
bless  Grod  for  the  important  discovery !  May  the 
benefit  thereof  be  diffused  over  the  whole  globe  !  May 
it  extend  to  the  latest  posterity  of  mankind,  and 
make  the  name  of  Franklin,  like  that  of  Newton, 
immortair 

Upon  a  review  of  what  has  been  advanced  in  the 
course  of  theSe  pages,  relative  to  the  nature  of 
thunderstorms  and  the  operation  of  lightning  rods, 
it  appears  that  buildings  and  other  elevations  are 
struck  and  damaged  by  lightning,  only  in  conse¬ 
quence  of  their  being  points  in  one  of  the  termi¬ 
nating  planes  of  a  great  electrical  disturbance  in  the 
atmosphere ;  not  from  any  property  of  attraction  for 
the  matter  of  lightning,  inherent  in  the  substances  of 
which  such  elevations  are  composed : — that  light¬ 
ning  rods  remove,  by  the  aptness  of  their  parts,  the 
resistance  experienced  by  the  electrical  discharge  in 
moving  through  less  perfect  conducting  matter; 


190 


CONCLUDING  OBSERVATIONS. 


and  hence,  by  allowing  a  rapid  and  free  neutraliza¬ 
tion  of  the  opposite  electrical  powers,  they  prevent 
the  damage  attendant  on  an  obstructed  action : — ■ 
that  the  operation  of  such  rods,  being  of  a  purely 
passive  kind,  they  can  no  more  be  said  to  invite  or 
draw  down  lightning  upon  the  buildings  to  which 
they  are  applied,  than  a  rain-pipe  can  be  said  to 
draw  down  or  invite  the  rain  which  flows  through 
it: — that  such  a  passive  property  cannot  be  fairly 
adduced  as  an  argument  against  their  general  use : — 
that  since  lightning  rods  only  operate  in  transmit¬ 
ting  as  much  electricity  as  falls  on  them,  they  can¬ 
not  be  prejudicial  to  buildings,  but  must,  on  the 
contrary,  by  a  rapid  annihilation  either  of  the  whole 
or  a  part  of  the  force  in  action,  necessarily  contribute 
to  security  : — that  lightning,  being  nothing  more 
than  the  electrical  discharge  moving  through  bad 
conducting  matter,  under  an  explosive  form,  the 
tendency  of  a  lightning  rod  is  to  deprive  the  dis¬ 
charge  of  this  form  from  the  instant  it  falls  on  the 
point  of  the  rod,  and  by  converting  it  into  an 
evanescent  current,  through  matter  calculated  to 
assist  its  progress,  to  annihilate  it  as  lightning 
altogether. 

In  the  treatment  of  this  question,  it  was  not  pos¬ 
sible  to  avoid  a  frequent  appeal  to  electrical  action, 
on  the  great  scale  of  nature.  If,  therefore,  the  re¬ 
markable  instances  quoted,  of  lightning  striking  on 
buildings  and  ships,  should  appear  to  be  somewhat 
numerous,  and  to  be  treated  of  in  too  great  detail, 
yet  it  must  be  recollected,  that  it  is  only  by  pursu- 


CONCLUDING  OBSERVATIONS. 


191 


ing  such  a  course  that  we  can  hope  to  arrive  at  de¬ 
ductions  worthy  of  confidence.  Hence  it  is,  that  in 
the  progress  of  these  inquiries  we  have  been  led  to 
adhere  carefully  to  a  series  of  well-authenticated 
facts,  and  by  keeping  strictly  within  the  safe  path  of 
inductive  science,  we  have  endeavored  to  throw  some 
further  light  on  a  subject  of  very  great  public  im¬ 
portance,  which  has  not  been  generally  or  fully  ap¬ 
preciated.  With  respect  to  certain  prejudiced  views 
and  opinions  which  have  been  entertained  of  the 
operation  of  lightning  rods,  we  trust  to  have  made 
it  appear  that  such  opinions  are  founded  on  no 
sound  basis  whatever,  and  that  a  judicious  applica¬ 
tion  of  pointed  conductors,  both  on  land  and  at  sea, 
is  not  only  desirable,  but  is,  in  a  great  variety  of 
cases,  quite  essential  to  the  preservation  of  buildings 
and  ships  from  the  ravages  of  lightning. 


THE  END. 


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